A METHOD OF PASSIVATING SURFACE EFFECTS IN METAL OXIDE LAYERS AND DEVICES COMPRISING THEREOF

Abstract

The present invention relates to a method of producing a metal oxide layer on a substrate, to a method of producing an optoelectronic device or an electrochemical device and to an optoelectronic device comprising a metal oxide layer.

Claims

1. A method of producing a solar cell, said method comprising producing a metal oxide layer on a substrate by providing a substrate into a deposition chamber; heating said substrate at a predefined temperature for a predefined period of time and maintaining said heating; introducing at least one carrier gas and at least one reacting gas comprising oxygen gas; sputtering said metal oxide layer under a ratio of said carrier gas and said reacting gas, thereby forming said metal oxide layer of a desired thickness; cooling said sputtered substrate to a preferred temperature and under a flow of at least one processing gas, such as said at least one carrier gas or said at least one reacting gas, for a preferred period of time, wherein said predefined period of time is between 1 and 120 minutes, thereby preventing formation of, or passivating possible surface defects of said sputtered metal oxide layer; depositing a layer of light harvesting material onto said metal oxide layer; depositing a contact layer onto said layer of light harvesting material; depositing a metal contact onto said contact layer.

2. A method according to claim 1, wherein said predefined temperature is between 100? C. and 600? C., such as at 150? C., such as at 350? C.

3. A method according to claim 1, wherein said at least one carrier gas comprises argon.

4. A method according to claim 1, wherein said metal oxide is titanium oxide (TiO.sub.x).

5. A method according to claim 1, wherein said ratio is between 1% to 50% of reacting gas over reacting gas and carrier gas, such as 25%.

6. A method according to claim 1, wherein said preferred temperature is lower than 100? C.

7. A method according to claim 1, further comprising maintaining a pressure between 5?10.sup.?2 and 3?10.sup.?4 mbar while sputtering.

8. A method according to claim 1, wherein said flow of said at least one processing gas is between 1 and 20 sccm, such as 5 sccm at a preferred pressure between 10.sup.?4 mbar and 10.sup.?2 mbar, such as 10.sup.?3 mbar.

9. A method according to claim 1, wherein said deposition chamber is an ultra-high vacuum sputter deposition chamber.

10. A method according to claim 1, wherein said substrate is a transparent conductive substrate.

11. A solar cell, produced according to the method according to claim 1.

12. A solar cell, such as a non-fullerene acceptor based organic solar cell, comprising: a transparent conductive substrate; an electron transport layer (ETL) located onto said transparent conductive substrate, such as a metal oxide layer produced on a substrate by providing a substrate into a deposition chamber; heating said substrate at a predefined temperature for a predefined period of time and maintaining said heating; introducing at least one carrier gas and at least one reacting gas comprising oxygen gas; sputtering said metal oxide layer under a ratio of said carrier gas and said reacting gas, thereby forming said metal oxide layer of a desired thickness; cooling said sputtered substrate to a preferred temperature and under a flow of at least one processing gas, such as said at least one carrier gas or said at least one reacting gas, for a preferred period of time, wherein said predefined period of time is between 1 and 120 minutes, thereby preventing formation of, or passivating possible surface defects of said sputtered metal oxide layer, a layer of light harvesting material, such as a combination of light harvesting organic materials; a hole transport layer (HTL) located onto said layer of light harvesting material; a metal contact located onto said HTL.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0069] The method of producing a metal oxide layer, an optoelectronic device or an electrochemical device and the optoelectronic device comprising a metal oxide layer of the invention will now be described in more details with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0070] FIG. 1 is a flow chart of the method of producing a metal oxide layer according to some embodiments of the invention.

[0071] FIG. 2 is a flow chart of the method of producing an optoelectronic device or an electrochemical device according to some other embodiments of the invention.

[0072] FIG. 3 is a schematic illustration of an organic solar cell according to some embodiments of the invention comprising PBDB-T:ITIC as donor/acceptor light harvesting composition.

[0073] FIG. 4 is a schematic illustration of an organic solar cell according to some embodiments of the invention comprising perovskite as light harvesting material.

[0074] FIG. 5 is a graph showing current-voltage characteristics of a solar cells having a configuration as described in FIG. 4.

[0075] FIG. 6 is a graph showing the External Quantum Efficiency (EQE) vs wavelength for solar cells having a configuration as described in FIG. 4.

[0076] FIG. 7 is a graph showing the evolution of normalized Power Conversion Efficiency (PCE) (stability), over time at 1 sun light illumination and at Room Temperature (RT), i.e. between 20 and 25? C., of the solar cells having a configuration as described in FIG. 4.

[0077] FIG. 8 is a graph showing the evolution of normalized PCE (stability), over time at 1 sun light illumination and at RT, for two solar cells, one using the titanium dioxide layer of the invention and a configuration as in FIG. 4, the other one using a standard ZnO layer in a correspondent configuration.

DETAILED DESCRIPTION OF AN EMBODIMENT

[0078] FIG. 1 is a flow chart of the method 1 of producing a metal oxide layer on a substrate.

[0079] The method 1 comprises the steps of: [0080] S1, providing a substrate into a deposition chamber; [0081] S2, heating the substrate at a predefined temperature for a predefined period of time and maintaining the heating; [0082] S3, introducing at least one carrier gas and at least one reacting gas; [0083] S4, sputtering the metal oxide layer under a ratio of the carrier gas and the reacting gas, thereby forming the metal oxide layer of a desired thickness; [0084] S5, cooling the sputtered substrate to a preferred temperature and under a flow of at least one processing gas for a preferred period of time, thereby preventing formation of, or passivating possible surface defects of the sputtered metal oxide layer.

[0085] FIG. 2 is a flow chart of the method 2 of producing an optoelectronic device or an electrochemical device.

[0086] The method 2 comprises the steps of: [0087] S6, producing a metal oxide layer on a substrate according to method 1; [0088] S7, depositing a layer of light harvesting material onto the metal oxide layer; [0089] S8, depositing a contact layer onto the layer of light harvesting material; [0090] S9, depositing a metal contact onto the contact layer.

[0091] FIG. 3 is a schematic illustration of an organic solar cell 8 according to some embodiments of the invention.

[0092] The organic solar cell 8 comprises a conductive glass substrate 7 coated with a thin layer of ITO. A Ti oxide layer 6 of few nanometers is deposited onto the ITO layer 6 according to the method of the first aspect of the invention.

[0093] A layer of PBDB-T:ITIC 5 is spin coated onto the Ti oxide layer 6.

[0094] Optimal thickness may be achieved by repeated spin coating at predetermined speed and for a predetermined period of time.

[0095] A further layer of MoO.sub.34 is deposited onto the PBDB-T:ITIC and a Ag contact layer 3 is finally deposited by, for example, thermal evaporation.

[0096] FIG. 4 is a schematic illustration of an organic solar cell 17 according to some embodiments of the invention.

[0097] The organic solar cell 17 has a glass substrate 16 coated with a thin layer of ITO 15. A TiO.sub.2 layer 14, 15 nm thick, is sputtered onto the conductive substrate according to the method of the first aspect of the invention.

[0098] A layer of perovskite 13 is deposited, by, for example, spin coating, onto the Ti oxide layer 14.

[0099] A passivation layer 12 is deposited onto the perovskite layer 13 to further suppress defects of the perovskite polycrystalline layer 13.

[0100] A further layer of Spiro-OMeTAD 11 as HTL material is further deposited onto the passivation layer 12 and a Au contact layer 10 is finally deposited by, for example, thermal evaporation.

[0101] FIG. 5 is a graph showing current-voltage (IV) characteristics of the solar cell 17 described by FIG. 4.

[0102] The graph compares the IV curves of a solar cell having the configurations as in FIG. 4 in which a layer of TiO.sub.2 is deposited either through standard processing, i.e. line 18, through the method of the invention in which TiO.sub.2 is sputtered keeping the temperature of the substrate at 150 ?C, i.e. line 19 or through the method of the invention in which TiO.sub.2 is sputtered keeping the temperature of the substrate at 350? C., i.e. line 20.

[0103] FIG. 6 is a graph showing the External Quantum Efficiency (EQE) vs wavelength of solar cell 17 as described in FIG. 4.

[0104] The graph compares as in FIG. 5, performances of a solar cell having the configurations as in FIG. 4 in which a layer of TiO.sub.2 is deposited either through standard processing, i.e. line 22, through the method of the invention in which TiO.sub.2 is sputtered keeping the temperature of the substrate at 150 ?C, i.e. line 23 or through the method of the invention in which TiO.sub.2 is sputtered keeping the temperature of the substrate at 350 ?C, i.e. line 21.

[0105] Clearly better performances of energy conversion can be observed for the solar cell having a 15 nm TiO.sub.2 layer sputtered through the method of the invention keeping the temperature of the substrate at 350 ?C.

[0106] FIG. 7 is a graph comparing the evolution of normalized PCE (stability) for a solar cell as described in FIG. 4 in which the layer of TiO.sub.2 is deposited either through standard processing, i.e. line 25, or through the method of the invention in which TiO.sub.2 is sputtered keeping the temperature of the substrate at 350 ?C, i.e. line 24.

[0107] From FIG. 7 it can be noticed that, through the method of the invention, the life time of the solar cell is improved as, after 5 days, the PCE of the solar cell sample having a 15 nm TiO.sub.2 layer sputtered through the method of the invention is almost three times higher than the one of the solar cell sample in which the layer of TiO.sub.2 is deposited through standard processing.

[0108] FIG. 8 is a graph showing the evolution of normalized PCE (stability) for two solar cell, one using the TiO.sub.2 of the invention, i.e. line 27 in a configuration as in FIG. 4, the other one using a standard ZnO layer, i.e. line 26 in a correspondent configuration.

[0109] Also in this case, through the method of the invention, the lifetime of the solra cell is improved as, after 14 days, the sample produced according to the method of the invention showed a normalized PCE of 60% compared to a PCE of 35% for a solar cell having a standard ZnO layer.

[0110] Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms comprising or comprises do not exclude other possible elements or steps. In addition, the mentioning of references such as a or an etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.