A TWO-TERMINAL DEVICE

Abstract

There is provided a two-terminal device, including a substrate comprising a first cell having a first characteristic resistance, and a second cell, spaced apart from the first cell along the web direction of the substrate, having a second characteristic resistance; a first terminal and a second terminal, each terminal being formed towards or at opposing edges of the substrate across the transverse direction, and each terminal being in electrical communication with the first cell and the second cell; and a connecting portion, between the first cell and the second cell, the connecting portion having a third characteristic resistance; wherein the third characteristic resistance is greater than or equal to at least one of the first characteristic resistance and the second characteristic resistance. There is also provided a method of forming such a two-terminal device).

Claims

1. A two-terminal device, including a substrate comprising: a first cell having a first characteristic resistance, and a second cell, spaced apart from the first cell along a web direction of the substrate, having a second characteristic resistance; a first terminal and a second terminal, each terminal being formed towards or at opposing edges of the substrate across a transverse direction, and each terminal being in electrical communication with the first cell and the second cell; a connecting portion, between the first cell and the second cell, the connecting portion providing electrical connectivity between the first cell and the second cell, and having a third characteristic resistance; wherein the third characteristic resistance is greater than both the first characteristic resistance and the second characteristic resistance, such that an electrical charge from the first or second cell is extractable at the first terminal or the second terminal in preference to transferring between the first cell and the second cell across the connecting portion.

2. (canceled)

3. A two-terminal device according to claim 1, wherein the third characteristic resistance is at least two times greater than at least one of the first characteristic resistance and the second characteristic resistance.

4. A two-terminal device according to claim 1, wherein the connecting portion comprises at least one resistive element, wherein the at least one resistive element comprises at least one of a peak of the substrate and/or a rutted portion of the substrate.

5. (canceled)

6. A two-terminal device according to claim 4, wherein the at least one resistive element comprises a channel in the substrate, wherein the channel is formed as a depression, an indentation, or an etch in the substrate.

7. (canceled)

8. A two-terminal device according to claim 6, wherein the first cell comprises a first series of grooves and/or the second cell comprises a second series of grooves, wherein the channel transects a portion of the first series of grooves and/or a portion of the second series of grooves, wherein the portion where the channel transects the first series of grooves and/or the second series of grooves is located towards an end of each groove.

9. (canceled)

10. A two-terminal device according to claim 4, wherein the at least one resistive element comprises a plurality of channels in the substrate.

11. (canceled)

12. A two-terminal device according to claim 10, wherein the first cell comprises a first series of grooves and/or the second cell comprises a second series of grooves, and wherein each channel of the plurality of channels transects a portion of the first series of grooves and/or a portion of the second series of grooves, wherein the portion where the channels transects the first series of grooves and/or the second series of grooves is located towards an end of each groove.

13. (canceled)

14. A two-terminal device according to claim 10, wherein the plurality of channels comprises a first channel, having a first channel characteristic resistance, a second channel, having a second channel characteristic resistance, and a third channel, having a third characteristic resistance, wherein the first channel characteristic resistance, the second channel characteristic resistance, and the third channel characteristic resistance provide substantially all of the third characteristic resistance.

15. (canceled)

16. A two-terminal device according to claim 6, wherein the channel or each channel of the plurality of channels is substantially Z-shaped having a predetermined angle.

17. (canceled)

18. A two-terminal device according to claim 10, wherein the first cell comprises a first series of grooves and the second cell comprises a second series of grooves, the substrate further comprising: a first transection channel that transects each channel of the plurality of channels at a distal end of each channel and transects a portion of the first series of grooves; and a second transection channel that transects each channel of the plurality of channels at a proximal end of each channel and transects a portion of the second series of grooves.

19. A two-terminal device according to claim 18, wherein the first transection channel and/or the second transection channel transect the portion of the first series of grooves and/or the portion of the second series of grooves towards an end of each groove.

20. (canceled)

21. A two-terminal device according to claim 18, wherein each channel of the plurality of channels, the first transection channel and the second transection channel form a substantial Z-shape having a predetermined angle.

22. (canceled)

23. A two-terminal device according to claim 6, wherein the channel has an aspect ratio of at least 1:1.6.

24. A method of forming a two-terminal device, comprising: providing a substrate; forming a first cell within the substrate, the first cell having a first characteristic resistance; forming a second cell within the substrate, spaced apart from the first cell along a web direction of the substrate, the second cell having a second characteristic resistance; forming a first terminal and a second terminal, each terminal being formed towards or at opposing edges of the substrate across the web direction, and at least one of the first terminal and/or the second terminal being formed in electrical connection with the first cell and the second cell; forming a connecting portion, between the first cell and the second cell, the connecting portion providing electrical connectivity between the first cell and the second cell, and having a third characteristic resistance; wherein the third characteristic resistance is greater than both the first characteristic resistance and the second characteristic resistance, such that an electrical charge from the first or second cell is extracted at the first terminal or the second terminal in preference to transferring from the first cell to the second cell across the connecting portion.

25. A method according to claim 24, wherein: the step of forming a first cell comprises forming a first series of grooves within the substrate; the step of forming a second cell comprises forming a second series of grooves within the substrate; and the step of forming a connecting portion comprises forming at least one channel within the connecting portion; the method further comprising: coating a first face of at least one of each groove of the first series of grooves, each groove of the second series of grooves, and/or the at least one channel with a first material; coating a second face of at least one of each groove of the first series of grooves, each groove of the second series of grooves, and/or the at least one channel with a second material; and at least partially filling each groove of the first series of grooves, each groove of the second series of grooves and the at least one channel with a third material; wherein the third material is a perovskite structured material.

26. A method according to claim 24, wherein: the step of forming a first cell comprises forming a first series of grooves in the substrate; the step of forming a second cell comprises forming a second series of grooves; and the method further comprising at least partially filling each groove of the first series of grooves and the second series of grooves with a third material, thereby forming an electrical connection across each groove of the first series of grooves, and an electrical connection across each groove of the second series of grooves; wherein the third material is a perovskite structured material.

27. A two-terminal device according to claim 1, wherein the first cell comprises at least one first groove and/or the second cell comprises at least one second groove, wherein the at least one first groove and/or the at least one second groove is at least partially filled with a third material, wherein the third material comprises one of a capacitor material, a supercapacitor material, a dielectric material, and/or a perovskite structured material.

28. A two-terminal device according to claim 27, wherein the at least one first groove and/or the at least one second groove is coated with a first material on a first face and/or is coated with a second material on a second face.

29. A two-terminal device according to claim 28, wherein the third material contacts the first material coated on the first face and/or the second material coated on the second face.

30. A two-terminal device according to claim 28, wherein the first material comprises at least one of a non-insulating material, a conductor material, a semiconductor material, and/or an electron transfer layer.

31. A two-terminal device according to claim 28, wherein the second material comprises at least one of a non-insulating material, a conductor material, a semiconductor material, and/or a hole transport layer.

32. A two-terminal device according to claim 27, wherein the third material comprises a perovskite structured material, and wherein the perovskite structured material has a general chemical structure of ABX3, where A and B are two different cations of different sizes, and X is an anion that chemically bonds to both A and B.

33. A two-terminal device according to claim 32, wherein the perovskite structured material has an optical bandgap between 1.1 eV and 2.5 eV.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0366] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[0367] FIG. 1 illustrates an electrical diagram of a two-terminal device in accordance with the prior art;

[0368] FIG. 2 illustrates (a) an electrical diagram of a two-terminal device in accordance with the invention and (b) an enlarged view of a portion of the electrical diagram of (a);

[0369] FIG. 3 illustrates a plan view of a substrate in accordance with one embodiment of the invention;

[0370] FIG. 4 illustrates a plan view of a substrate in accordance with one embodiment of the invention;

[0371] FIG. 5 illustrates a plan view of a substrate in accordance with one embodiment of the invention;

[0372] FIG. 6 illustrates a plan view of a substrate in accordance with one embodiment of the invention;

[0373] FIG. 7 illustrates (a) a plan view of a substrate in accordance with one embodiment of the invention and (b) a plan view of another substrate in accordance with one embodiment of the invention;

[0374] FIG. 8 illustrates (a) an enlarged top view of the substrate of FIG. 5, (b) an enlarged perspective view of the substrate of FIG. 5, (c) another enlarged top view of the substrate of FIG. 5, and (d) an enlarged perspective view of the transection region of the substrate of FIG. 5;

[0375] FIG. 9 illustrates (a) an enlarged perspective view of the substrate of FIGS. 7(a), and (b) an enlarged perspective view of the transection region of the substrate of FIG. 7(a);

[0376] FIG. 10 illustrates a cross-sectional view of a groove, a transection region and a channel of a substrate in accordance with one embodiment of the invention;

[0377] FIG. 11 illustrates a cross-sectional view of a groove, a transection region and a channel of a substrate in accordance with one embodiment of the invention;

[0378] FIG. 12 illustrates a method of forming a substrate in accordance with one embodiment of the invention;

[0379] FIG. 13 illustrates a method of forming a substrate in accordance with one embodiment of the invention;

[0380] FIG. 14 illustrates a method of forming a two-terminal device in accordance with one embodiment of the invention;

[0381] FIG. 15 illustrates a coating process of the method of FIG. 14;

[0382] FIG. 16 illustrates a two-terminal device in accordance with one embodiment of the invention;

[0383] FIG. 17 illustrates a cross-section view of a two-terminal device according to one embodiment of the present invention;

[0384] FIG. 18 illustrates a cross-section view of a two-terminal device according to another embodiment of the present invention;

[0385] FIG. 19 illustrates a cross-section view of a two-terminal device according to a further embodiment of the present invention;

[0386] FIG. 20 illustrates a cross-section view of a two-terminal device according to another embodiment of the present invention;

[0387] FIG. 21 illustrates a cross-section view of a two-terminal device according to a still further embodiment of the present invention;

[0388] FIG. 22 illustrates a cross-section view of a two-terminal device according to another embodiment of the present invention;

[0389] FIG. 23 illustrates a graph comparing the performances of the two-terminal device of FIG. 1 with the two-terminal device of FIGS. 2(a) and 3;

[0390] FIG. 24 illustrates a graph depicting the performance of a two-terminal device as described herein; and

[0391] FIG. 25 illustrates yet another graph depicting the performance of a two-terminal device as described herein.

DETAILED DESCRIPTION

[0392] Like reference numerals are used to depict like features throughout.

[0393] Various modifications to the detailed designs are described above are envisaged. For example, any number of grooves within any number of series of grooves may be used. Equally, any number of delineation features, such as channels, transection channels or the like may be used. Moreover, any combination of such delineation features may be used.

[0394] It will be clear to a person skilled in the art that features described in relation to any of the embodiments described above can be application interchangeably between the different embodiments. The embodiments described above are examples to illustrate various features of the invention.

[0395] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Through the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0396] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect embodiment, or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract or drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0397] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0398] FIGS. 2(a) and 2(b) illustrate an example of a two-terminal device 50 having a substrate, in accordance with the present invention. The substrate includes a first cell 54a, a second cell 54b and a third cell 54c. The first, second and third cells 54a, 54b, 54c may be photovoltaic cells as shown in FIGS. 2(a) and 2(b). In this specific example, the first, second and third cells 54a, 54b, 54c are formed as a first series of grooves 54a, a second series of grooves 54b and a third series of grooves 54c. Each series of grooves 54a, 54b, 54c includes a plurality of grooves.

[0399] As shown in FIGS. 2(a) and 2(b), grooves are connected in series with one another to form a first series of grooves 54a. Likewise, grooves are connected in series to form a second series of grooves 54b, and further grooves are connected in series to form a third series of grooves 54c. In this way, the grooves of a respective series of grooves 54a, 54b, 54c is first connected in series to form each of the respective series of grooves 54a, 54b, 54c, and then each series of grooves 54a, 54b, 54c is connected in parallel to one another. Thus, the two-terminal device 50 of FIGS. 2(a) and 2(b) differs from that of the prior art as illustrated in FIG. 1.

[0400] The two-terminal device 50 of FIGS. 2(a) and 2(b) provides the advantage that bypass diodes, which are typically required in conventional substrates such as those illustrated in FIG. 1, are not necessary. Instead, grooves are placed in series relatively close to one another, in some examples with a spacing of approximately 0.1 mm or less between each groove, such that each groove within a series of grooves 54a, 54b, 54c experiences substantially, or exactly, the same lighting conditions, in use. Moreover, since each series of grooves 54a, 54b, 54c is connected in parallel, shading of grooves of an individual series of grooves 54a, 54b, 54c has a less significant impact on the overall performance of the device. Thus, the prerequisite of bypass diodes is negated in the present invention.

[0401] Furthermore, as shown in FIGS. 2(a) and 2(b), the two-terminal device 50 includes a first connecting portion including a first delineation feature 56a, and a second connecting portion including a second delineation feature 56b. The first delineation feature 56a is provided between the first series of grooves 54a and the second series of grooves 54b. the second delineation feature 54b is provided between the second series of grooves 54b and the third series of grooves 54c. Any number of grooves may be present in any number of series of grooves 54a, 54b, 54c having any number of delineation features 56a, 56b therebetween, as described herein. Further, the delineation feature 56a, 56b may take any appropriate form as discussed further herein.

[0402] Each series of grooves 54a, 54b, 54c provides an electrical connection between a first electrical connection 58 and a second electrical connection 60. The first electrical connection 58 is a positive electrical connection and the second electrical connection 60 is a negative electrical connection in the depicted embodiment. Alternatively, the first electrical connection 58 may be a negative electrical connection and the second electrical connection 60 may be a positive electrical connection. The positive and negative electrical connections 58, 60 may be connected to respective terminals, for example, positive and negative busbars 62, 64 of the two-terminal device 50. In this way, positive electrical charge is carried to the positive busbar 62 and negative electrical charge is carried to the opposing negative busbar 64. The busbars 62, 64 may be connected to another electrical element, such as a capacitor or the like.

[0403] As described herein, the delineation features typically serve to provide an electrical disconnection, or provide electrical isolation, between adjacent series of grooves. However, as described herein, this is oftentimes not possible, and so an electrical short occurs across one or more of the delineation features during manufacture of such devices. In this case, the inventors have surprisingly found that conductive delineations features 56a, 56b, that is delineation features that provide an electrical connection thereacross, can be modelled upon a resistor in parallel with a reverse-biased diode, as shown in FIG. 2(a). In this way, each delineation feature 56a, 56b provides a resistance such that the electrical pathway from a terminal groove of a series of grooves 54a, 54b, 54c to its adjacent electrical connection 58, 60 is favoured over the electrical pathway across the delineation feature 56a, 56b. Thus, electrical charge is extractable at positive and negative busbars 62, 64 in preference to electrical charge transfer across the delineation feature 56a, 56b, that is, a short circuit across the delineation feature 56a, 56b.

[0404] Furthermore, the inventors have surprisingly found that if the delineation feature 56a, 56b is conductive, said delineation feature 56a, 56b provides charge blocking and substantive electrical isolation between adjacent series of grooves simultaneously. That is, the delineation feature 56a, 56b provides charge blocking in the same orientation that would be used for a bypass diode. In this way, a conductive delineation feature 56a, 56b protects the adjacent series of grooves 54a, 54b, 54c from reverse bias damage, that is, from electrical charge flowing in a direction that is opposite to the flow of electrical charge across each groove within the series of grooves 54a, 54b, 54c. For example, referring to FIG. 2(b), the delineation feature 56a prevents electrical charge flowing from positive electrical connection 58, connected to positive busbar 62, through the delineation feature 56a and towards the grooves and the negative electrical connection 60, connected to the negative busbar 64. Thus, it has been found, much to the surprise of the inventors, that not only does a conductive delineation feature 56a, 56b allow for charge extraction as in non-conductive delineation features, but also that a conductive delineation feature 56a, 56b can provide protection against reverse bias damage.

[0405] FIG. 3 illustrates a plan view of a two-terminal device 100 comprising a substrate 102. The substrate 102 has a surface comprising a plurality of series of grooves 104a-104d. In particular, the substrate 102 comprises a first series of grooves 104a, a second series of grooves 104b, a third series of grooves 104c and a fourth series of grooves 104d. Further series of grooves may be provided in the machine direction MD of the substrate 102. Each groove of the series of grooves 104a-104d generally run in parallel to one another across the transverse direction TD of the substrate 102, extending from a proximal end, for example, proximal to a first terminal 112 as described below, to a distal end, for example, distal to the first terminal 112 as described below. A channel 106 is provided between each series of grooves 104a-104d.

[0406] The two-terminal device 100 may be an optoelectronic device, such as a solar photovoltaic cell. Such a two-terminal device 100 includes a mixture of interdigitated (parallel connected) and cascaded (series connected) grooves 104a-104d. The operating voltage of such a two-terminal device 100 can be controlled by changing the number of series of grooves 104a-104d. Increasing the number of series of grooves 104a-104d increases the operating voltage of the two-terminal device 100. Such a two-terminal device 100 can be operated in parallel or a combination of series and parallel arrangement. It may be an advantage of the two-terminal device 100 that this removes the need for extra process steps to be used to connect the cascaded groove structures in series to achieve the desired output voltage.

[0407] The channel 106 physically separates the cascaded (series connected) grooves 104a-104d. The channel 106 enables the cascaded grooves 104a-104d to be connected in parallel via electrical connection to first and second terminals 112, 114. In this way, it is possible to extract the desired electric charge generated at the voltage designed by the number of cascaded groove structures 104a-104d.

[0408] The channel 106, also referred to as the delineation or structural delineation feature, first crosses the first series of grooves 104a towards one end of the substrate 102 and then crosses a spacer 108 between the first series of grooves 104a and the second series of grooves 104b, and subsequently crosses the second series of grooves 104b towards the opposite edge of the substrate 102. Since many of these channels 106 are used, each series of grooves, 104a, 104b for example, are crossed toward each edge by elements of two successive individual channels 106, as shown in FIG. 3. The channel 106 crosses towards an end of each groove of the series of grooves 104a, 104b, 104c, 104d. However, in other embodiments, the channel 106 may terminate an end, i.e. cross at an end, of each groove of the series of grooves 104a, 104b, 104c, 104d.

[0409] Together, the spacers 108 and channels 106 divide the substrate 102 into a first area 110a and a second area 110b. The first area 110a carries a positive charge and the second area 110b carries a negative charge. The first area 110a terminates at a first or positive terminal 112 at one edge of the substrate 102, and the second area 110b terminates at a second or negative terminal 114 at the other, opposite, edge of the substrate 102, referring to the transverse direction TD. The first area 110a provides an electrical connection of the first groove of each series of grooves 104a-104d to the first terminal 112. The second area 110b provides an electrical connection of the last groove of each series of grooves 104a-104d to the second terminal 114. Thus, a two-terminal device 100 having a first terminal 112 and a second terminal 114 is formed.

[0410] FIG. 4 illustrates a plan view of another two-terminal device 200 comprising a substrate 202. The substrate 202 has a surface comprising a plurality of series of grooves 204a-204d. In particular, the substrate 202 comprises a first series of grooves 204a, a second series of grooves 204b, a third series of grooves 204c and a fourth series of grooves 204d. Further series of grooves may be provided in the machine direction MD of the substrate 202. Each groove of the series of grooves 204a-204d generally run in parallel to one another across the transverse direction TD of the substrate 202, extending from a proximal end, for example, proximal to a first terminal 212 as described below, to a distal end, for example, distal to the first terminal 212 as described below. A channel 206, in this case a plurality of channels 206a-206c, is provided between each series of grooves 204a-204d.

[0411] The two-terminal device 200 may be an optoelectronic device, such as a solar photovoltaic cell. Such a two-terminal device 200 includes a mixture of interdigitated (parallel connected) and cascaded (series connected) grooves 204a-204d. The operating voltage of such a two-terminal device 200 can be controlled by changing the number of series of grooves 204a-204d. Increasing the number of series of grooves 204a-204d increases the operating voltage of the two-terminal device 200. Such a two-terminal device 200 can be operated in parallel or a combination of series and parallel arrangement. It may be an advantage of the two-terminal device 200 that this removes the need for extra process steps to be used to connect the cascaded groove structures in series to achieve the desired output voltage.

[0412] Each channel of the plurality of channels 206a-206c physically separates the cascaded (series connected) grooves 204a-204d. Each of the plurality of channels 206a-206c enables the cascaded (series connected) grooves 204a-204d to be electrically connected in parallel to first and second terminals 212, 214. In this way, it is possible to extract the desired electric charge generated at the voltage designed by the number of cascaded groove structures 204a-204d.

[0413] The first channel 206a, also referred to as the first delineation or structural delineation feature, first crosses the first series of grooves 204a towards one end of the substrate 202 and then crosses a space 208 between the first series of grooves 204a and the second series of grooves 204b, and subsequently crosses the second series of grooves 204b towards the opposite edge of the substrate 202. Since many of these channels are used, each series of grooves, 204a, 204b for example, are crossed toward each edge by elements of two successive individual channels, as shown in FIG. 4. The first channel 206a crosses towards an end of each groove of the series of grooves 204a, 204b, 204c, 204d. However, in other embodiments, the first channel 206a may terminate an end, i.e. cross at an end, of each groove of the series of grooves 204a, 204b, 204c, 204d.

[0414] The second channel 206b, like the first channel 206a, first crosses the first series of grooves 204a towards one end of the substrate 202 and then crosses a spacer 208 between the first series of grooves 204a and the second series of grooves 204b, and subsequently crosses the second series of grooves 204b towards the opposite edge of the substrate 202. The third channel 206c crosses the first series of grooves 204a, the spacer 208, and the second series of grooves 204b, in the same manner as the first channel 206a and the second channel 206b.

[0415] It may be advantageous to use a plurality of channels 206a-206c to mitigate the likelihood of an electrical short forming across the interface between the first series of grooves 204a and the second series of grooves 204b, that is, across the plurality of channels 206a-206c. Thus, a plurality of channels 206a-206c ensure a more efficient and reliable two-terminal device 200.

[0416] Together, the spacers 208 and channels 206 divide the substrate 202 into a first area 210a and a second area 210b. The first area 210a carries a positive charge and the second area 210b carries a negative charge. The first area 210a terminates at a first or positive terminal 212 at one edge of the substrate 202, and the second area 210b terminates at a second or negative terminal 214 at the other, opposite, edge of the substrate 202, referring to the transverse direction TD. The first area 210a provides an electrical connection of the first groove of each series of grooves 204a-204d to the first terminal 212. The second area 210b provides an electrical connection of the last groove of each series of grooves 204a-204d to the second terminal 214. Thus, a two-terminal device 200 having a first terminal 212 and a second terminal 214 is formed.

[0417] FIG. 5 illustrates a plan view of yet another two-terminal device 300 comprising a substrate 302. The substrate 302 has a surface comprising a plurality of series of grooves 304a-304d. In particular, the substrate 302 comprises a first series of grooves 304a, a second series of grooves 304b, a third series of grooves 304c and a fourth series of grooves 304d. Further series of grooves may be provided in the machine direction MD of the substrate 302. Each groove of the series of grooves 304a-304d generally run in parallel to one another across the transverse direction TD of the substrate 302, extending from a proximal end, for example, proximal to a first terminal 312 as described below, to a distal end, for example, distal to the first terminal 312 as described below. A delineation feature (306a, 306b, 306c, 316, 318) is provided between each series of grooves 304a-304d.

[0418] The two-terminal device 300 may be an optoelectronic device, such as a solar photovoltaic cell. Such a two-terminal device 300 includes a mixture of interdigitated (parallel connected) and cascaded (series connected) grooves 304a-304d. The operating voltage of such a two-terminal device 300 can be controlled by changing the number of series of grooves 304a-304d. Increasing the number of series of grooves 304a-304d increases the operating voltage of the two-terminal device 300. Such a two-terminal device 300 can be operated in parallel or a combination of series and parallel arrangement. It may be an advantage of the two-terminal device 300 that this removes the need for extra process steps to be used to connect the cascaded groove structures in series to achieve the desired output voltage.

[0419] The delineation features (306a, 306b, 306c, 316, 318) physically separates the cascaded (series connected) grooves 304a-304d. The delineation features enables the cascaded (series connected) grooves 304a-304d to be connected in parallel via electrical connection to first and second terminals 312, 314, In this way, it is possible to extract the desired electric charge generated at the voltage designed by the number of cascaded groove structures 304a-304d.

[0420] The delineation feature comprises a plurality of channels, specifically a first channel 306a, a second channel 306b and a third channel 306c. Each channel 306a-306c is connected at their distal ends to a first transection channel 316, and connected at their proximal ends to a second transection channel 318. The first and second transection channels 316, 318 form part of the delineation feature and may be substantially channel-like, or may be further channels. The first and second transection channels 316, 318 generally connect to each channel 306a-306c perpendicularly at their respective ends. The first transection channel 316 first crosses the first series of grooves 304a towards one end of the substrate 302 and then crosses a spacer 308 between the first series of grooves 304a and the second series of grooves 304b, and subsequently crosses the second series of grooves 304b towards the opposite edge of the substrate 302. Since many of these delineation features are used, each series of grooves, 304a, 304b for example, are crossed toward each edge by elements of two successive transection channels 316, 318, as shown in FIG. 5. The delineation feature, specifically transection channels 316, 218 crosses towards an end of each groove of the series of grooves 304a, 304b, 304c, 304d. However, in other embodiments, the transection channels 316, 318 may terminate an end, i.e. cross at an end, of each groove of the series of grooves 304a, 304b, 304c, 304d.

[0421] It may be advantageous to use a plurality of channels 306a-306c between the series of grooves to mitigate the likelihood of an electrical short forming across the interface between the first series of grooves 304a and the second series of grooves 304b, that is, across the delineation feature. Furthermore, the described arrangement, specifically of transection channels 316, 318 at each end of each channel 306a-306c, may provide for an easier manufacture of such efficient and reliable substrates.

[0422] Together, the spacers 308 and the plurality of channels 306a-306c divide the substrate 302 into a first area 310a and a second area 310b. The first area 310a carries a positive charge and the second area 310b carries a negative charge. The first area 310a terminates at a first or positive terminal 312 at one edge of the substrate 302, and the second area 310b terminates at a second or negative terminal 314 at the other, opposite, edge of the substrate 302, referring to the transverse direction TD. The first area 310a provides an electrical connection of the first groove of each series of grooves 304a-304d to the first terminal 312. The second area 310b provides an electrical connection of the last groove of each series of grooves 304a-304d to the second terminal 314. Thus, a two-terminal device 300 having a first terminal 312 and a second terminal 314 is formed.

[0423] FIG. 6 illustrates a plan view of yet another two-terminal device 400 comprising a substrate 402. The substrate 402 has a surface comprising a plurality of series of grooves 404a-404c. In particular, the substrate 402 comprises a first series of grooves 404a, a second series of grooves 404b, and a third series of grooves 404c. Further series of grooves may be provided in the machine direction MD of the substrate 402. Each groove of the series of grooves 404a-404c generally run in parallel to one another across the transverse direction TD of the substrate 402, extending from a proximal end, for example, proximal to a first terminal 412 as described below, to a distal end, for example, distal to the first terminal 412 as described below. A channel 406 is provided between each series of grooves 404a-404c.

[0424] The two-terminal device 400 may be an optoelectronic device, such as a solar photovoltaic cell. Such a two-terminal device 400 includes a mixture of interdigitated (parallel connected) and cascaded (series connected) grooves 404a-404c. The operating voltage of such a two-terminal device 400 can be controlled by changing the number of series of grooves 404a-404c. Increasing the number of series of grooves 404a-404c increases the operating voltage of the two-terminal device 400. Such a two-terminal device 400 can be operated in parallel or a combination of series and parallel arrangement. It may be an advantage of the two-terminal device 400 that this removes the need for extra process steps to be used to connect the cascaded groove structures in series to achieve the desired output voltage.

[0425] The channel 406 physically separates the cascaded (series connected) grooves 404a-404c. The channel 406 enables the cascaded grooves 404a-404c to be connected in parallel via electrical connection to first and second terminals 412, 414. In this way, it is possible to extract the desired electric charge generated at the voltage designed by the number of cascaded groove structures 404a-404c.

[0426] The channel 406, also referred to as a delineation feature or structural delineation feature, comprises first region, extending along the machine direction MD, a second region extending along the machine direction MD and substantially parallel to the first region, and a third region therebetween extending along the transverse direction TD and connecting the first region to the second region. The channel 406 first crosses the first series of grooves 404a towards one end of the substrate 402 and then crosses a spacer 408 between the first series of grooves 404a and the second series of grooves 404b, and subsequently crosses the second series of grooves 404b towards the opposite edge of the substrate 402. Since many of these channels 406 are used, each series of grooves, 404a, 404b for example, are crossed toward each edge by elements of two successive channels 406, as shown in FIG. 6. The channel 406 terminates, i.e. crosses at, an end of each groove of the series of grooves 404a, 404b, 404c. However, in other embodiments, the channel 406 may cross towards an end, i.e. it may not terminate an end, of each groove of the series of grooves 404a, 404b, 404c.

[0427] Moreover, the channel 406 are substantially Z-shaped in the depicted embodiment. As shown in FIG. 6, a first predetermined angle, a, is formed between the first region of the channel 406 and the third region of the channel 406. A second predetermined angle, β, is formed between the second region of the channel 406 and the third region of the channel 406. In this example, α=β, however, in other examples, α≠β. In this specific example, α and β are approximately 70 degrees. α and β may have a different value in other examples, for example, any value between 1 degree and 179 degrees.

[0428] It may be desirable to use a Z-shaped channel 406 as this can be advantageous during the manufacture of such substrates. As described further below, such substrates are coated using off-axis directional coating methods. Thus, by providing an angle between the various regions of the channel 406, the shadowing effect is increased, thereby providing regions of the channel 406 that are not coated with material. In this way, the likelihood of a short circuit across the channel 406 is mitigated, as described further below.

[0429] Together, the spacers 408 and the channels 406 divide the substrate 402 into a first area 410a and a second area 410b. The first area 410a carries a positive charge and the second area 410b carries a negative charge. The first area 410a terminates at a first or positive terminal 412 at one edge of the substrate 402, and the second area 410b terminates at a second or negative terminal 414 at the other, opposite, edge of the substrate 402, referring to the transverse direction TD. The first area 410a provides an electrical connection of the first groove of each series of grooves 404a-404c to the first terminal 412. The second area 410b provides an electrical connection of the last groove of each series of grooves 404a-404c to the second terminal 414. Thus, a two-terminal device 400 having a first terminal 412 and a second terminal 414 is formed.

[0430] FIGS. 7(a) and 7(b) illustrates a plan view of yet another two-terminal device 500 comprising a substrate 502. The two-terminal device 500 of FIGS. 7(a) and 7(b) is similar in construction to the two-terminal device of FIG. 6. That is, the two-terminal device 500 includes a substrate 502, a plurality of series of grooves 504a-504d, a channel 506, a spacer 508, a first area 510a carrying a positive charge, a second area 510b carrying a negative charge, and first and second terminals 512, 514. These features are described in relation to FIG. 6 and are not discussed further here.

[0431] The two-terminal device 500 of FIGS. 7(a) and 7(b) differs from FIG. 6 in that the first and second predetermined angles α, β are formed differently. In FIG. 6, the third region of the channel 406 is angled and the first and second regions are substantially perpendicular to the series of grooves 404a-404c. However, as shown in FIG. 7(a), in the present example of the two-terminal device 500, the third region of the channel 506 extends substantially in parallel to the series of grooves 504a-504d, and the first and second regions are formed at an angle with respect to the third region. In the depicted example, α=β, however, in other examples, α≠β. In this specific example, α and β are approximately 45 degrees. In some examples (not shown), α and β may be greater than 90 degrees, for example, up to, but not including, 180 degrees. As shown in FIG. 7(b), the delineation feature may take any shape, having any angle, disposed in any appropriate manner on the substrate.

[0432] It may be desirable to use a Z-shaped channel 506 as this can be advantageous during the manufacture of such substrates. As described further below, such substrates are coated using off-axis directional coating methods. Thus, by providing an angle between the various regions of the channel 506, the shadowing effect is increased, thereby providing regions of the channel 506 that are not coated with material. In this way, the likelihood of a short circuit across the channel 506 is mitigated, as described further below. Moreover, the Z-shaped channel 506 may be preferred as it allows for a more efficient use of space between the series of grooves 504a-504d.

[0433] FIGS. 8(a) to 8(d) illustrate various views of the two terminal device 300 as shown in FIG. 5. Like numerals denote like features in FIGS. 8(a) to 8(d). As best shown in FIGS. 8(c) and 8(d), the two-terminal device 300 includes a series of grooves 304, each groove having a groove base 350. The delineation feature, specifically the transection channels 316, 318 of the delineation feature, each includes a channel base 354. As can be seen in FIGS. 8(a) to 8(d), and with further reference to FIGS. 10 and 11 as discussed below, the groove base 350 has a substantially constant depth across the elongate width of the grooves 304. Additionally, the groove base 350 tends towards the channel base 354 in a transection region 352. That is, the depth of each groove of the grooves 304 tends towards the depth of the delineation feature, or channel, in this example the transection channels 316, 318, within a transection region 352. This is described in further detail below, with reference to FIGS. 10 and 11.

[0434] FIGS. 9(a) and 9(b) illustrate various views of the two-terminal device 500 as shown in FIG. 7(a). Like numerals denote like features in FIGS. 9(a) and 9(b). The two-terminal device 500 includes a series of grooves 504, each groove having a groove base 550. The delineation feature, specifically the channel 506, includes a channel base 554. As best shown in FIG. 9(b), and with further reference to FIGS. 10 and 11 as discussed below, the groove base 550 has a substantially constant depth across the elongate width of the grooves 504. Additionally, the groove base 550 tends towards the channel base 554 in a transection region 552. That is, the depth of each groove of the grooves 504 tends towards the depth of the delineation feature, in this example, the channel 506, within a transection region 552. This is described in further detail below, with reference to FIGS. 10 and 11.

[0435] FIG. 10 illustrates a cross-sectional view of one example of a transection region between a groove and a channel that can be applied to any of the examples discussed herein. Specifically, FIG. 10 shows a substrate 602 having a groove 604 of a series of grooves, and a channel 606. The channel 606 transects the groove 604 at its proximal end. The groove 604 includes a groove base 650, and the channel 606 includes a channel base 654.

[0436] The groove 604, specifically the groove base 650, tends towards the channel 606, specifically the channel base 654, in a transection region 652. The transection region 652 has a transection region base 656 that is substantially arcuate in the example shown. That is, the transection region base 656 has a variable depth as it tends from the groove base 650 to the channel base 654. The variable depth is non-linear in the depicted example.

[0437] FIG. 11 illustrates another example of a transection region between a groove and a channel that can be applied to any of the examples discussed herein. Specifically, FIG. 11 shows a substrate 702 having a groove 704, of a series of grooves, and a channel 706. The channel 706 transects the groove 704 at its proximal end. The groove 704 includes a groove base 750, and the channel 706 includes a channel base 754.

[0438] The groove 704, specifically the groove base 750, tends towards the channel 706, specifically the channel base 754, in a transection region 752. The transection region 752 has a transection region base 756 that is substantially linear, or straight, in the example shown. That is, the transection region base 756 has a variable depth as it tends from the groove base 750 to the channel base 754. The variable depth is linear in the depicted example.

[0439] As shown in FIG. 11, the linear transection region 752 forms an angle γ with respect to an imaginary axis, formed as a continuation of the groove base 750. The angle γ is shown as approximately 45 degrees in the depicted example. However, other angles may be used.

[0440] FIG. 12 illustrates a method 800 of forming a substrate as described herein. The method 800 includes the step of providing 810 a web of flexible material, forming 820 a first series of grooves within the web of flexible material, forming 830 a second series of grooves within the web of flexible material, and forming 840 a channel between the first series of grooves and the second series of grooves within the web of flexible material.

[0441] The respective steps 810, 820, 830, 840 may be carried out sequentially, that is in an order. For example, the steps 810, 820, 830, 840 may be carried out in the order as described in FIG. 12. Alternatively, the steps 810, 820, 830, 840 may be carried out in any other order. For example, the step of forming 840 the channel may take place between forming 820 the first series of grooves and forming 830 the second series of grooves. Further, two or more, or all, of steps 810, 820, 830, 840 may be carried out simultaneously, or concurrently, that is at the same time. For example, the steps of forming 820 the first series of grooves, forming 830 the second series of grooves, and forming 840 the channel may all take place simultaneously.

[0442] The step of forming 840 the channel further includes forming the channel such that the channel transects a portion of the first series of grooves and the second series of grooves towards a proximal end of each groove. Furthermore, the step of forming 840 the channel includes forming a depth of each groove that tends towards the depth of the channel at the proximal end of each groove.

[0443] In some examples, one or more of the steps of forming 820 a first series of grooves, forming 830 a second series of grooves and forming 840 a channel therebetween includes an embossing process, as described in relation to FIG. 13.

[0444] FIG. 13 illustrates a specific method 900 of forming a substrate as described herein. The method 900 may be a specific example of the method 800 of FIG. 12, for example, the method 900 may represent an embossing process. The method 900 starts by providing 910 a web of flexible material 902. The method 900 also includes the step of coating 920 the web of flexible material 902 with a UV-curable composition, thereby forming a UV-curable coating 904 on at least one surface of the web of flexible material 902. The method may also include the step of engaging 930 the coated web of flexible material (902, 904) with a shim, shown in this particular example as a master shim being a cylindrical stamping roll 906. In other examples, there may be a plurality of shims, a single master shim, or a stamping plate formed as one or more of the plurality of shims or as the single master shim. That is, the skilled person would recognise that the shim need not be a master shim, nor need it be a cylindrical stamping roll 906. In the example shown, the cylindrical stamping roll 906 includes a series of protrusions 908. The protrusions 908 correspond to the first series of grooves, the second series of grooves and the channel, as described further below.

[0445] As the protrusions 908 engage the coated web of flexible material (902, 904), the UV-curable coating 904 is at least partially UV-cured 940 during the engagement step 930. The protrusions 908 are then removed 950 from the coated web of flexible material (902, 904). As the protrusions 908 are removed 950, the coated web of flexible material (902, 904) is caused to be drawn towards the protrusions 908 of the cylindrical stamping roll 906 as they are removed 950, due to the partial UV-curing of the UV-curable coating 904. However, since the UV-curable coating 904 is only partially UV-cured, that is not fully cured, the coated web of flexible material (902, 904) then relaxes as the protrusions 908 of the cylindrical stamping roll 906 are fully removed. In this way, the transection region between the first series of grooves or the second series of grooves and the channel is first caused to be drawn upwardly, towards the cylindrical stamping roll 906, and then relaxes, such that the transection region is formed in a manner such that the depth of the grooves tends towards the depth of the channel, as described above.

[0446] The cylindrical stamping roll 906 is continually rolled 960 across the machine direction MD of the coated web of flexible material (902, 904). Thus, the process is repeated along the machine direction MD. It may also be desirable to cut the formed substrate at various intervals along the machine direction MD. In such cases, the method 900 may optionally include the step of cutting the master substrate into a plurality of substrates.

[0447] FIG. 14 illustrates a method 1000 of forming a two-terminal device having a substrate as described herein. The method 1000 may be a continuation of method 800 of FIG. 12 or method 900 of FIG. 13. The method 1000 starts by providing, or forming, 1010 a substrate 1001 as described herein. The method 1000 may also include coating 1020 a first face 1002 of a first series of grooves 1006, a second series of grooves 1008 and a channel 1011 with a first material 1012. The method 1000 may also include coating 1040 a second face 1004 of the first series of grooves 1006, the second series of grooves 1008 and the channel 1010 with a second material 1014. The first material 1012 and the second 1014 may be different.

[0448] The coating steps 1020, 1040 may comprise an off-axis directional coating as best shown in FIGS. 14, and 15(a) to 15(c). That is, the coating steps 1020, 1040 may comprise coating at an angle formed with respect to the plane of the substrate 1001. As shown in FIG. 15, such an angle δ may be in the range of 30 to 70 degrees, for example approximately 45 degrees.

[0449] FIGS. 15(a) and 15(b) illustrate a coating process, of the substrates FIGS. 10 and 11, respectively. FIG. 15(c) further illustrates a comparison coating process without having the transection regions of FIGS. 10 and 11 as described. FIGS. 15(a) and 15(b) illustrate a coating process having an incident coating angle θ. The arrow C illustrates the incoming coating of a material. As shown, the transection region 652, 752, tending from the groove depth 650, 750 to the channel depth 654, 754, as described above, ensures that a large proportion of the transection region 652, 752, that is the region connecting the grooves 604, 704 to the channel 606, 706, is shadowed, indicated by the region below arrow C, by the wall W of the channel 606, 706 during the coating process. In this way, during the coating process, a large proportion of the transection region 652, 752 is not coated with an incoming material. Thus, once the grooves 604, 704 and the channel 606, 706 are filled with a material that allows for an electrical pathway, as described below, the lack of coated material in the transection region 652, 752 ensures that there is no electrical connection between the grooves 604, 704 and the channel 606, 706.

[0450] In comparison, referring to FIG. 15(c), without the transection regions 652, 752 that tend from the groove depth to the channel depth as described, the interface between an adjacent series of grooves 780 and the channel 790 is coated with material at the same incident coating angle δ as in FIGS. 15(a) and 15(b). That is, in the example of FIG. 15(c), the creation of an electrical short during manufacture is solely dependent upon the amount of material to be filled in the grooves 780 and the channel 790. This is known to be difficult to control. Whereas, electrical shorts are mitigated through the use of a transection region in which the groove depth tends to the channel depth, thus increasing the shadowing of the region between the grooves and the channel during manufacture.

[0451] The method 1000 further includes the step of at least partially filling 1060 the channel 1010 with a third material 1016. The third material 1016 may be different to the first material 1012 and the second material 1014. In some examples, the step of at least partially filling 1060 the channel 1010 may comprise a printing process. In addition to the channel 1010 being filled with a third material 1016, the first series of grooves 1006, the second series of grooves 1008, or both the first and second series of grooves 1006, 1008 may be at least partially filled with the same third material 1016, as shown in FIG. 14. FIG. 14 illustrates an embodiment in which the channel 1004 is filled, or completely filled, with the third material 1016.

[0452] The first material 1012, the second material 1014 and the third material 1016 vary depending on the intended use of the two-terminal device that is to be formed. For example, in some cases it may be desirable to produce a solar photovoltaic device that can supply electricity to a device. In this example, the first material 1012 may be a non-insulating material, such as a conductor or a semiconductor, the second material 1014 may be a non-insulating material, such as a conductor or a semiconductor, and the third material 1016 may be a perovskite structured material. As would be recognised by the person skilled in the art, the two-terminal device can be produced with the appropriate coatings that are suitable for the intended final use of the two-terminal device to be produced.

[0453] FIG. 16 illustrates a two-terminal device 1100 including a substrate 1102 as described herein. The substrate 1102 includes a first series of grooves 1104, a second series of grooves 1106 and a channel 1108 therebetween. The channel 1108 may have a greater depth than that of the grooves 1104, 1106, as shown.

[0454] The first series of grooves 1104 include a first face 1104a, a second, opposing, face 1104b, and a cavity 1104c therebetween. The second series of grooves 1106 include a first face 1106a, a second, opposing, face 1106b, and a cavity 1106c therebetween. The channel 1108 includes a first face 1108a, a second, opposing, face 1108b, and a cavity 1108c therebetween. The first faces 1104a, 1106a, 1108a are coated with a first material 1110. The second face 1104b, 1106b, 1108b are coated with a second material 1112. Additionally, a third material 1114 is provided within the cavities 1104c, 1106c, 1108c. As shown in FIG. 16, the cavities 1104c, 1106c of the first and second series of grooves 1104, 1106 are filled to the extent that the first material 1110 and the second material 1112 on opposing faces (1104a, 1104b and 1106a, 1106b) are in contact with the third material 1114. In this way, an electrical pathway is formed across the first series of grooves 1104 and the second series of grooves 1106.

[0455] As can be seen in FIG. 16, the cavity 1108c of the channel 1108 is filled with the third material 1114 such that the third material 1114 is in contact with the first material 1110 on the first face 1108a or the second material 1112 on the second face 1108b. Thus, an electrical pathway is provided. However, due to the nature of the substrate described herein and the methods of formation thereof, the cavity 1108c of the channel 1108 could be filled with the third material 1114 to a lesser extent. Thus, even if the cavity 1108c is filled to a large extent as shown, it would not make contact with the first material 1110 or the second material 1112 within the transection region in which the grooves 1104, 1106 meet with the channel 1108. In this way, an electrical pathway, and thus an electrical short, is prevented across the channel 1108, whilst allowing for a more simple manufacturing process.

[0456] FIG. 17 illustrates a two-terminal device 1200. The two-terminal device 1200 includes a substrate 1202. The substrate 1202 has a first cell and a second cell that is spaced apart from the first cell. The second cell is spaced from the first cell along the substrate 1202 along the web direction of the substrate 1202. The first cell is provided with a first series of grooves 1204. Each of the first series of grooves 1204 include a first face 1204a, a second, opposing, face 1204b, and a cavity 1204c therebetween. The second cell is provided with a second series of grooves 1206. Each of the second series of grooves 1206 include a first face 1206a, a second, opposing, face 1206b, and a cavity 1206c therebetween. A connecting portion including a first channel 1208 and a second channel 1209 is provided between the first cell and the second cell. The first channel 1208 has a first face 1208a, a second, opposing, face 1208b, and a cavity 1208c therebetween. The second channel 1209 is provided between the first channel 1208 and the second cell. The second channel 1209 has a first face 1209a, a second, opposing, face 1209b, and a cavity 1209c therebetween. In other examples, one channel 1208 is provided between the first cell and the second cell. In other additional examples, more than two channels 1208, 1209 are provided between the first cell and the second cell. The substrate 1202 is provided with a first terminal and a second terminal. The first and second terminals are formed at opposing edges of the substrate 1202 across the transverse direction of the substrate 1202. The first and second terminals are electrically connected to the first cell and the second cell in a manner similar to that described in relation to FIGS. 3 to 7. That is, the first and second terminals are in electrical communication with each of the first cell and the second cell. In some examples, one, or both, of the cavities 1208c, 1209c may be filled to the extent that the third material 1214 within those cavities 1208c, 1209c contact the first material 1210 and the second material 1212 to provide an electrical connection thereacross. However, due to the combined resistance of the channels 1208, 1209, as discussed further below, charge from the first or second cell is extracted at the first and second terminals of the device rather than being transferred across the connecting portions 1208, 1209.

[0457] The first faces 1204a, 1206a, 1208a, 1209a are coated with a first material 1210. The second faces 1204b, 1206b, 1208b, 1209b are coated with a second material 1212. Additionally, a third material 1214 is provided within the cavities 1204c, 1206c, 1208c, 1209c. The cavities 1204c, 1206c of the first and second series of grooves 1204, 1206 are filled to the extent that the first material 1210 and the second material 1212 on opposing faces (1204a, 1204b and 1206a, 1206b) are in contact with the third material 1214. This forms an electrical pathway across the first series of grooves 1204 of the first cell, and between the second series of grooves 1206 of the second cell.

[0458] The cavity 1208c of the first channel 1208 is partially filled with the third material 1214 such that the third material 1214 in the cavity 1208c does not contact the first material 1210 on the first face 1208a and the second material 1212 on the second face 1208b. No electrical pathway is provided between the third material 1214 and the first material 1210 on the first face 1208a. No electrical pathway is provided between the third material 1214 and the second material 1212 on the second face 1208b. The cavity 1209c of the second channel 1209 is partially filled with the third material 1214 such that the third material 1214 in the cavity 1209c does not contact the first material 1210 on the first face 1209a and the second material 1212 on the second face 1209b. No electrical pathway is provided between the third material 1214 and the first material 1210 on the first face 1209a. No electrical pathway is provided between the third material 1214 and the second material 1212 on the second face 1209b. The first and second channels 1208, 1209 ensure there is an electrical resistance from one side of the connecting portion to the other.

[0459] In use, the combined resistance across the first and second channels 1208, 1209, that is the resistance across the connecting portion, is greater than the resistance across the first cell. The combined resistance across the first and second channels 1208, 1209 is greater than the resistance across the second cell. More specifically, the first cell has a first characteristic resistance. The second cell has a second characteristic resistance. The combined resistance across the first and second channels 1208, 1209 is a third characteristic resistance that is greater than the first characteristic resistance across the first cell. The third characteristic resistance is greater than the second characteristic resistance across the second cell. By having a combined resistance across the first and second channels 1208, 1209 that is greater than the resistance across the first cell and the second cell, charge is extracted from the first and second terminals, rather than being transferred across between the first cell and the second cell, across the connecting portion. In this particular example, the resistance value of the first characteristic resistance and the value of the second characteristic resistance are the same. It is envisaged that in some examples, the third characteristic resistance across the connecting portion is equal to at least one of the first characteristic resistance and the second characteristic resistance. It is envisaged that more than two channels 1208, 1209 may be provided between the first cell and the second cell. By providing multiple channels between the first cell and the second cell, the combined resistance is increased with the number of channels. The space between the channels may be increased to further increase the combined resistance across the connecting portion. In this particular example, the combined resistance across the connecting portion is five times the resistance across the first cell. In this particular example, the resistance across the connecting portion is also five times the resistance across the second cell. The resistance across the first cell and across the second cell are the same in this particular example.

[0460] FIG. 18 illustrates a two-terminal device 1300. The two-terminal device 1300 includes a substrate 1302. The substrate 1302 has a first cell 1304, a second cell 1306, a first terminal and a second terminal as previous described with reference to FIG. 17 and thus will not be described again in detail. Like numerals apply with respect to FIG. 17, except in that in FIG. 18 they begin with the digits “13” instead of “12”. A connecting portion is provided between the first cell 1304 and the second cell 1306. The connecting portion includes a number of channels. In this particular example, the connecting portion is provided with two channels 1308, 1309 that are filled with the third material 1314 as described in relation to FIG. 17. As will be noted, FIG. 18 is identical to that of FIG. 17, except in that the channels within the connecting portion are filled, such that an electrical connection is made between the first material 1310 on one side of each channel, and the second material 1312 on the other side of each channel. Thus, an electrical pathway is formed thereacross.

[0461] In use, the resistance across the connecting portion is greater than the resistance across the first cell 1304. The resistance across the connecting portion is also greater than the resistance across the second cell 1306. More specifically, the first cell has a first characteristic resistance. The second cell has a second characteristic resistance. The resistance across the connecting portion is a third characteristic resistance that is greater than the first characteristic resistance across the first cell 1304. The third characteristic resistance is also greater than the second characteristic resistance across the second cell 1306. By having an arrangement where the resistance across the connecting portion is greater than the first characteristic resistance across the first cell 1304 and greater than the second characteristic resistance across the second cell 1306, charge is extracted from the first and second terminals, rather than being transferred across the first and second terminals. In this particular example, the third characteristic resistance is three times the first characteristic resistance across the first cell 1304. The third characteristic resistance is there times the second characteristic resistance across the second cell 1306. In some examples, the connecting portion is additionally provided with a resistive element (not shown) that increases the resistance across the connecting portion.

[0462] FIG. 19 illustrates a two-terminal device 1400. The two-terminal device 1400 includes a substrate 1402 that has a first cell 1404 and a second cell 1406 substantially as previously described with reference to FIG. 17, and therefore will not be described here again in detail. Substrate 1402 is provided with a first terminal and a second terminal substantially as previously described with reference to FIG. 17, and therefore will not be described here again in detail. A connecting portion 1408 is provided between the first cell 1404 and the second cell 1406. In this particular example, the connecting portion 1408 is a planar element extending from and between the first series of grooves forming the first cell 1404 and the second series of groves forming the second cell 1406. The connecting portion 1408 extends between the first cell 1404 and the second cell 1406 in the direction along the web direction of the substrate 1402. The first series of grooves include a first face 1404a, a second, opposing, face 1404b, and a cavity 1404c therebetween. The second series of grooves include a first face 1406a, a second, opposing, face 1406b, and a cavity 1406c therebetween. The first faces 1404a, 1406a are coated with a first material 1410. The second faces 1404b, 1406b are coated with a second material 1412. The second material 1412 coating the second face 1404b of the groove 1404 proximal the connecting portion 1408 partially coats the connecting portion 1408.

[0463] The first material 1410 coating the first face 1406a of the groove 1404 proximal the connecting portion 1408 partially coats the connecting portion 1408. In this way, the connecting portion 1408 provided between the first cell 1404 and the second cell 1406 is partially coated with a second material 1412 on the end of the connecting portion 1408 proximal the first cell 1404. The connecting portion 1408 provided between the first cell 1404 and the second cell 1406 is partially coated with a first material 1410 on the end of the connecting portion 1408 proximal the second cell 1406. The connecting portion 1408 is therefore provided between the first cell 1404 and the second cell 1406, partially coated with a second material 1412 on a first end proximal the first cell 1404, and is partially coated with a first material 1410 on a second end proximal the second cell 1406. The first material 1410 and the second material 1412 partially coating the connecting portion 1408 are electrically separated from one another. The connecting portion 1408 ensures an electrical resistance from one side to the other.

[0464] In use, the resistance across the connecting portion 1408 is greater than the resistance across the first cell 1404. The resistance across the connecting portion 1408 is greater than the resistance across the second cell 1406. The first cell 1404 has a first characteristic resistance. The second cell 1406 has a second characteristic resistance. The resistance across the connecting portion 1408 is a third characteristic resistance that is greater than the first characteristic resistance across the first cell 1404. The third characteristic resistance is greater than the second characteristic resistance across the second cell 1406. The arrangement of having a greater resistance across the connecting portion 1408 between the first cell 1404 and the second cell 1406 allows charge from the first or second cell to be extracted from the first and second terminals, rather than being transferred between the first cell 1404 and the second cell 1406, across the connecting portion 1408.

[0465] FIG. 20 illustrates a two-terminal device 1500. The two-terminal device 1500 includes a substrate 1502. The substrate 1502 has a first cell 1504 and a second cell 1504 spaced apart from the first cell 1504 along the substrate 1502 along the web direction of the substrate 1502. The first cell 1504 and the second cell 1506 are as previously described with reference to FIG. 17, and therefore will not be described here again in detail. The substrate 1502 is provided with a first terminal and a second terminal as described with reference to FIG. 17, and therefore will also not be described here again in detail. A connecting portion is provided between the first cell 1504 and the second cell 1506. The connecting portion includes a channel 1508 provided with a first face 1508a, a second, opposing, face 1508b, and a cavity 1508c therebetween. The channel 1508 has a depth that is greater than the grooves of each of the first cell 1504 and the second cell 1506.

[0466] The first faces 1504a, 1506a, 1508a are coated with a first material 1510. The second faces 1504b, 1506b, 1508b are coated with a second material 1512. Additionally, a third material 1514 is provided within the cavities 1504c, 1506c, 1508c. The cavities 1504c, 1506c of the first cell 1504 and second cell 1506 respectively are filled to the extent that the first material 1510 and the second material 1512 on opposing faces (1504a, 1504b and 1506a, 1506b) are in contact with the third material 1514. This forms an electrical pathway across the first cell 1504, and across the second cell 1506.

[0467] Unlike the two-terminal device shown in FIG. 14, in which the cavity is fully filled by a material 1016, the walls, formed by faces 1508a, 1508b, of the cavity 1508c are coated with the third material 1514. The coating of the cavity 1508c is such that the third material 1514 in the cavity 1508c is electrically connected to the first material 1510 on the first face 1508a, and the second material 1512 on the second face 1508b. An electrical pathway is therefore provided between the first material 1510 on the first face 1508a of the connecting portion 1508, and the second material 1512 on the second face 1508b of the connecting portion 1508. The channel 1508 creates an electrical connection from one side to the other. That is, the channel 1508 electrically connects one side, proximal the first cell 1504, from the other side, proximal the second cell 1506.

[0468] In use, the resistance across the connecting portion is greater than the resistance across the first cell 1504. The resistance across the connecting portion is greater than the resistance across the second cell 1506. The first cell 1504 has a first characteristic resistance. The second cell 1506 has a second characteristic resistance. The resistance across the connecting portion is a third characteristic resistance that is greater than the first characteristic resistance across the first cell 1504. The third characteristic resistance is greater than the second characteristic resistance across the second cell 1506. This arrangement allows charge from the first or second cell to be extracted from the first and second terminals, rather than being transferred between the first cell 1504 and the second cell 1506, across the connecting portion 1508.

[0469] FIG. 21 illustrates a two-terminal device 1600. The two-terminal device 1600 includes a substrate 1602 having a first cell 1604, a second cell 1606, a first terminal and a second terminal, as hereinbefore described with reference to FIG. 20, and therefore will not be described here again in detail. A connecting portion including channel 1608 is provided between the first cell 1604 and the second cell 1606. The channel 1608 is provided with a first face 1608a proximal the first cell 1604, and a second, opposing face 1608b proximal the second cell 1606. The channel 1608 is provided with a cavity 1608c between the first face 1608a and the second face 1608b. The first face 1608a of the channel 1608 and the second face 1608b of the channel 1608 extend a depth into the substrate 1602 greater than the depth of the grooves of the first cell 1604 and second cell 1606. In this particular example, the channel 1608 is substantially U-shaped, having the first face 1608a, the second face 1608b, and a bottom rutted portion. In this example, the bottom rutted portion is formed of eight undulations. The cavity 1608c of the channel 1608 is larger in size in comparison to the cavities 1604c, 1606c of the first cell 1604 and the second cell 1606 respectively. The greater size and the depth of the channel 1608 in comparison with the grooves of the first cell 1604 and the second 1606 provide a greater resistance across the connecting portion relative to the resistance across the first cell 1604 and the second cell 1606 respectively.

[0470] The first faces 1604a, 1606a, 1608a are coated with a first material 1610. The second faces 1604b, 1606b, 1608b are coated with a second material 1612. Additionally, a third material 1614 is provided within the cavities 1604c, 1606c, 1608c. The cavities 1604c, 1606c of the first cell 1604 and the second cell 1606 respectively, are filled to the extent that the first material 1610 and the second material 1612 on opposing faces (1604a, 1604b and 1606a, 1606b) are in contact with the third material 1614. This forms an electrical pathway across the grooves of the first cell 1604, and between the grooves of the second cell 1606.

[0471] In this particular example, each of the grooves of the bottom rutted portion, forming the cavity 1608c, is partially filled, for example coated, with the third material 1614. In this way, the third material 1614 forms a coating, or a conformed coating or a film, of the third material 1614 within the undulations of the channel 1608. Thus, the third material 1614 is in contact with the first material 1610 on the first face 1608a. The third material 1614 also contacts the second material 1612 on the second face 1608b. An electrical pathway is provided between the third material 1614 and the first material 1610 on the first face 1608a. An electrical pathway is provided between the third material 1614 and the second material 1612 on the second face 1608b. The connecting portion provides an electrical connection from one side to the other. That is, the connecting portion provides an electrical connection from one side of the connecting portion proximal the first cell 1604, to the other side of the connecting portion proximal the second cell 1606.

[0472] In use, the resistance across the connecting portion is greater than the resistance across the first cell 1604. The resistance across the connecting portion is also greater than the resistance across the second cell 1606. The first cell 1604 has a first characteristic resistance. The second cell 1606 has a second characteristic resistance. The resistance across the connecting portion has a third characteristic resistance that is greater than the first characteristic resistance across the first cell 1604. The third characteristic resistance across the connecting portion is greater than the second characteristic resistance across the second cell 1606. By having a resistance across the connecting portion that is greater than the resistance across the first cell 1604 and the second cell 1606, charge from the first or second cell is extracted from the first and second terminals, rather than being transferred across between the first cell 1604 and the second cell 1606.

[0473] FIG. 22 illustrates a two-terminal device 1700. The two-terminal device 1700 includes a substrate 1702. The substrate 1702 has a first cell 1704 and a second cell 1706 spaced apart from the first cell 1704 along the substrate 1702 along the web direction of the substrate 1702. The first cell 1704 and the second cell 1706 are as previously described with reference to FIG. 20, and therefore will not be described here again in detail. The substrate 1702 is provided with a first terminal and a second terminal. The first and second terminals are formed at opposing edges of the substrate 1702 across the transverse direction of the substrate 1702. The first and second terminals are electrically connected to the first cell 1704 and the second cell 1706. That is, the first and second terminals are in electrical communication with each of the first cell 1704 and the second cell 1706.

[0474] A connecting portion, including a peak 1708 of the substrate 1702 is provided between the first cell 1704 and the second cell 1706. The peak 1708 is provided with a first face 1708a and a second, opposing, face 1708b. In this example, the peak 1708 is directed upwards, in a direction opposite to the direction of the grooves of the first cell 1704 and the second cell 1706. The first face 1708a of the peak 1708 is provided on a side proximal the first cell 1704. The second face 1708b of the peak 1708 is provided on a side proximal the second cell 1706. The peak 1708 has a height that is greater than the depth of the grooves of each of the first cell 1704 and the second cell 1706. In this particular example, the peak 1708 is formed from a block material. having a first material disposed on the first face 1708a and a second material disposed on the second face 1708b. This first and second materials disposed thereon may be the same as the first and second material 1710, 1712 disposed on the faces 1704a, 1704b, 1706a, 1706b of the cells 1704, 1706 as described below. In particular, the first face 1708a may be coated with non-insulating material, such as a conductor. In particular, the second face 1708b may be coated with non-insulating material, such as a conductor. There may be a region between the first face 1708a, 1708b in which no material is provided, such as a gap. This may be provided by removing a portion of the materials provided on the first face 1708a and the second face 1708b. Alternatively, such a portion may be masked during manufacturing. Further, in other embodiments, the upper portion of the block material may be removed after coating the first face 1708a and the second face 1708b, thereby providing an electrical resistance, between the respective faces. In this example, the connecting portion does not have a cavity. The connecting portion includes a peak at an end distal the grooves of the first cell 1704 and the second cell 1706.

[0475] The first faces 1704a, 1706a of the first cell 1704 and second cell 1706 respectively, are coated with a first material 1710. The second faces 1704b, 1706b of the first cell 1704 and second cell 1706 respectively, are coated with a second material 1712. Additionally, a third material 1714 is provided within the cavities 1704c, 1706c of the first cell 1704 and second cell 1706 respectively. The cavities 1704c, 1706c are filled to the extent that the first material 1710 and the second material 1712 on opposing faces (1704a, 1704b and 1706a, 1706b) are in contact with the third material 1714. This forms an electrical pathway across the first cell 1704, and across the second cell 1706.

[0476] In use, the resistance across the connecting portion is greater than the resistance across the first cell 1704. The resistance across the connecting portion is greater than the resistance across the second cell 1706. The first cell 1704 has a first characteristic resistance and the second cell 1706 has a second characteristic resistance. The resistance across the connecting portion is a third characteristic resistance that is greater than the first characteristic resistance across the first cell 1704. The third characteristic resistance is greater than the second characteristic resistance across the second cell 1706. This arrangement allows charge from the first or second cell to be extracted from the first and second terminals, rather than being transferred between the first cell 1704 and the second cell 1706, across the connecting portion.

[0477] FIG. 23 illustrates a comparison between the two-terminal device described in relation to FIG. 1 (“parallel first”) and the two-terminal device described in relation to FIGS. 2(a) and 3 (“series first (with delin)”). FIG. 23 illustrates the performance of each device as a function of electrical short probability per groove section. The performance of a device is defined as a percentage or a fraction of incoming light energy converted into electrical energy (PCE). As can be seen in FIG. 23, the performance of the two-terminal device described in FIGS. 2(a) and 3 is far superior to that of the two-terminal device described in FIG. 1. In particular, the device of FIGS. 2(a) and 3 remains at a high operational performance even at high short probabilities per groove section. On the other hand, the operational performance of the device of FIG. 1 rapidly decreases with an increasing short probability per groove section. In this way, the two-terminal device as described herein has a superior performance over the prior art.

[0478] FIG. 24 illustrates the performance, specifically the fraction of optimal performance with respect to a two-terminal device without a delineation feature, as a function of the resistance of the delineation feature, specifically measured as a multiple of the characteristic resistance of the delineation feature with respect to the characteristic resistance of the adjacent grooves, for a two-terminal device described herein. As shown in FIG. 24, as the characteristic resistance of the delineation feature, that is the connecting portion, is increased with respect to the characteristic resistance of the adjacent grooves, the performance of the device tends towards the expected ideal performance.

[0479] FIG. 25 illustrates the performance, specifically the fraction of optimal performance with respect to a two-terminal device without a delineation feature, as a function of the delineation short-circuit current, as a fraction of the current within a series of grooves. In particular, as described herein, the delineation feature acts as a reverse biased diode, and so the open-circuit voltage created is unimportant, as the operating voltage flows in the opposite direction. This is shown by the linear relationship between these functions, as demonstrated in FIG. 25.

[0480] It will be appreciated by persons skilled in the art that the above embodiment(s) have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departing from the scope of the invention as defined by the appended claims. Various modifications to the detailed designs as described above are possible, for example, variations may exist in number, shape, size, arrangement, assembly or the like. For example, any number of grooves and any number of series of grooves may be used, any number of channels, or delineation features, may be used. Further, the channel(s) may intersect the grooves at any appropriate angle and may be shaped in any appropriate way. Further, various grooves, channels, connecting portions or the like may be partially filled, filled, completely filled, or coating, as described herein. Mere reference to coating or filling in one embodiment does not preclude the possibility of filling or coating, respectively, the feature of said embodiment.