Silicon dioxide solar cell

Abstract

In order to increase the generation efficiency of a silicon dioxide solar cell, two conductive substrates are arranged so that the conductive surfaces thereof face each other, at least one of the substrates is disposed upon the substrate facing the light entry-side substrate, and an electrolyte is filled between the silicon dioxide particles compact and the light entry-side substrate. Silicon dioxide solar cells having this configuration exhibit a significantly increased short circuit current and open circuit voltage in comparison to solar cells in which the silicon dioxide and the electrolyte are mixed. This configuration can further be improved by disposing a titanium dioxide solar cell or a dye-sensitized titanium dioxide solar cell upon the light entry-side substrate to further increase the short circuit current and the open circuit voltage.

Claims

1. A silicon dioxide solar cell, comprising: first and second substrates having electrical conductivity, the first substrate having a negative electrode, the second substrate having a positive electrode, respectively, the first and second substrates being arranged so that the negative and positive electrodes of the first and second substrates are facing each other, the first substrate being a transparent substrate on a light incident side to which a light is irradiated; a layer made of silicon dioxide particles; and an electrolyte disposed between said first and second electrodes, wherein said layer made of silicon dioxide particles is disposed at the positive electrode on a side of the second substrate, a space between said layer made of silicon dioxide particles and said first substrate on the light incident side is filled with said electrolyte, and the silicon dioxide solar cell is configured to generate electricity from the silicon dioxide particles in said layer made of silicon dioxide particles.

2. The silicon dioxide solar cell according to claim 1, wherein the silicon dioxide particles have the particle diameter of 500 nm or less.

3. The silicon dioxide solar cell according to claim 1, wherein the silicon dioxide particles are treated with halogen acid.

4. The silicon dioxide solar cell according to claim 3, wherein the halogen acid is hydrofluoric acid.

5. The silicon dioxide solar cell according to claim 3, wherein the halogen acid is hydrochloric acid.

6. The silicon dioxide solar cell according to claim 1, wherein said layer made of silicon dioxide particles comprises silicon dioxide particles selected from the group consisting of synthetic quartz particles, fused quartz glass particles, borosilicate glass particles, and soda-lime glass particles.

7. The silicon dioxide solar cell according to claim 1, wherein a porous titanium dioxide sintered material is disposed on said negative electrode of the first substrate on the light incident side.

8. The silicon dioxide solar cell according to claim 7, wherein the porous titanium dioxide sintered material has adsorbed thereon sensitizing dye.

9. The silicon dioxide solar cell according to claim 1, wherein the silicon dioxide solar cell is capable of electricity generation from said layer made of silicon dioxide particles in response to a light which does not contain ultraviolet.

10. The silicon dioxide solar cell according to claim 1, wherein the positive electrode is a platinum electrode.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows diagrammatic views of a conventional porous titanium dioxide solar cell and dye-sensitized porous titanium dioxide solar cell.

(2) FIG. 2 shows a diagrammatic view of the prior art silicon dioxide solar cell.

(3) FIG. 3 shows a diagrammatic view of the silicon dioxide solar cell according to Embodiment 1.

(4) FIG. 4 shows a diagrammatic view of the solar cell according to Embodiment 2 using porous titanium dioxide and silicon dioxide.

(5) FIG. 5 shows a diagrammatic view of the solar cell according to Embodiment 3 using dye-sensitized porous titanium dioxide and silicon dioxide.

(6) FIG. 6 shows a voltage-current characteristics graph of the dye-sensitized porous titanium dioxide solar cell according to Embodiment 3 and a conventional dye-sensitized porous titanium dioxide solar cell.

(7) FIG. 7 shows a diagrammatic view of the arrangement of the silicon dioxide solar cell according to Embodiment 4 using pulverized silicon dioxide particles.

(8) FIG. 8 shows a diagrammatic view of the arrangement of the solar cell according to Embodiment 5 using porous titanium dioxide and pulverized silicon dioxide particles.

(9) FIG. 9 shows a diagrammatic view of the arrangement of the solar cell according to Embodiment 6 using dye-sensitized porous titanium dioxide and pulverized silicon dioxide particles.

(10) FIG. 10 shows a diagrammatic view of the arrangement of the solar cell according to Embodiment 7 using porous titanium dioxide and pulverized silicon dioxide particles.

(11) FIG. 11 shows a diagrammatic view of the arrangement of the solar cell according to Embodiment 8 using dye-sensitized porous titanium dioxide and pulverized silicon dioxide particles.

DESCRIPTION OF EMBODIMENTS

(12) Hereinbelow, modes for carrying out the invention will be described with reference to the accompanying drawings.

Embodiment 1

(13) FIG. 3 shows the silicon dioxide solar cell according to Embodiment 1, which is obtained by improving the silicon dioxide solar cell shown in FIG. 2.

(14) In FIG. 3, numerals 11 and 17 represent glass substrates having a transparent conductive layer 12 made of FTO or the like and a transparent conductive layer 16 made of FTO or the like, formed thereon respectively. The transparent conductive layer 12 and transparent conductive layer 16 function as an electrode for extracting electric power. The glass substrates 11 and 12 are arranged so that the transparent conductive layer 12 on the glass substrate 11 and the FTO layer 16 on the glass substrate 17 are facing each other.

(15) Numeral 20 represents a silicon dioxide (SiO.sub.2) calcinated material having the thickness of 0.15 to 0.20 mm, which is disposed on the glass substrate 17 on the side where light does not enter.

(16) On the transparent conductive layer 16 on the silicon dioxide side, a platinum (Pt) layer 15 is formed as an electrode for extracting charges.

(17) Numeral 14 represents an electrolyte. In contrast to the prior art silicon dioxide solar cell shown in FIG. 2 in which the electrolyte is mixed into silicon dioxide, the space between the silicon dioxide calcinated material 20 and the glass substrate 11 on the light incident side is filled with the electrolyte.

(18) Numeral 18 represents a sealing material, and numeral 19 represents an external load.

(19) In the electrolyte 14, there used an electrolyte obtained by adding 0.1 mol of LiI, 0.05 mol of I.sub.2, 0.5 mol of 4-tert-butylpyridine, and 0.5 mol of tetrabutylammonium iodide to 0.5 mol acetonitrile solvent.

(20) With respect to the silicon dioxide calcinated material 20, there is used a material obtained by immersing synthetic quartz which is crystalline silicon dioxide, or glass particles of quartz glass, non-alkali glass, borosilicate glass, soda-lime, or the like, which are amorphous, in a 5% aqueous solution of hydrofluoric acid for 5 minutes, washing the particles with water, drying them, and then pulverizing the resultant particles so that the particle diameter becomes 500 nm or less.

(21) With respect to the aqueous solution in which the silicon dioxide is immersed, hydrochloric acid can be used as halogen acid other than hydrofluoric acid.

(22) The synthetic quartz particles having the particle diameter of about 0.2 to 0.5 mm can be used, and those which are not calcined but are mixed with ethanol and applied onto the platinum electrode 15 and dried can also be used.

(23) The light entered from the light incident side glass substrate 11 enters the silicon dioxide 20 to cause electric generation.

(24) Using a solar simulator, the solar cell according to Embodiment 1 was irradiated with the light at 1 kw/m.sup.2 which is a solar constant. When the particle diameter of the synthetic quartz was 0.2 mm or less, a short-circuit current of 85 μA and an open circuit voltage of 470 mV were obtained. When the particle diameter was 500 nm or less, a short-circuit current of 348 μA and an open circuit voltage of 620 mV were obtained.

(25) These values have been drastically increased with respect to both the short-circuit current and open circuit voltage, as compared to the values of the prior art silicon dioxide solar cell shown in FIG. 2, although the measurement conditions are different from those for the embodiment.

(26) In addition, with respect to the synthetic quartz solar cell which is a silicon dioxide solar cell, the present inventors measured a short-circuit current at the illuminance almost equivalent to that of direct sunlight using a 300 W incandescent lamp which is a light source containing no ultraviolet region component. As a result, an open circuit voltage of 400 mV and a short-circuit current of 0.5 μA were obtained, which has confirmed that the silicon dioxide solar cell causes electric generation using solely the infrared light.

(27) From the above, it is apparent that the silicon dioxide solar cell causes electric generation also using the light containing no ultraviolet region component, where it is impossible for a dye-sensitized titanium dioxide solar cell which is a typical wet-type solar cell.

Embodiment 2

(28) Embodiment 2 is described with reference to FIG. 4.

(29) The solar cell according to Embodiment 2 is a combination of the silicon dioxide solar cell according to Embodiment 1 and the conventional titanium dioxide solar cell shown in FIG. 1(a) in a tandem configuration.

(30) In FIG. 4, numeral 11 represents a transparent substrate made of glass or a resin, forming on one surface thereof a transparent electrode layer 12 made of FTO or the like, which serves as an electrode on a light incident side. Numeral 3 represents a porous titanium dioxide solidified by a method, such as sintering. Numeral 14 represents an electrolytic solution, where an iodine electrolyte having iodine dissolved in an aqueous potassium iodide solution is generally used.

(31) Numeral 20 represents synthetic quartz particles having the particle diameter of 0.2 mm or less, which are mixed with ethanol and applied onto an electrode 25 made of platinum or the like and dried.

(32) Numeral 16 represents a transparent electrode made of FTO or the like, and numeral 17 represents a substrate made of glass or a resin. Numeral 18 represents a sealing material, and numeral 19 represents an external load.

(33) The ultraviolet light entered from the transparent substrate 11 on the light incident side enters the porous titanium dioxide 3 to cause electric generation, and the ultraviolet light and visible light which do not contribute to the electric generation enter the silicon dioxide 20 to cause electric generation.

(34) Thus, the solar cell according to Embodiment 2 can utilize light in the region from the ultraviolet light through the visible light in electric generation.

(35) When the solar cell according to Embodiment 1 is irradiated with light at 1 kw/m2, which is a solar constant, using a solar simulator, a short-circuit current of 20 μA and an open circuit voltage of 417 mV are obtained.

Embodiment 3

(36) Embodiment 3 is described with reference to FIG. 5.

(37) The solar cell according to Embodiment 3 is a combination of the silicon dioxide solar cell according to Embodiment 1 and the conventional dye-sensitized titanium dioxide solar cell shown in FIG. 1(b) in a tandem configuration.

(38) In FIG. 5, numeral 11 represents a transparent substrate made of glass or a resin, forming on one surface thereof a transparent conductive layer 12 made of FTO or the like, which serves as an electrode on a light incident side.

(39) Numeral 10 represents a porous titanium dioxide which is solidified by a method, such as sintering, and which has adsorbed thereon a sensitizing dye, such as a ruthenium complex dye.

(40) Numeral 14 represents an electrolytic solution, and an iodine electrolyte having iodine dissolved in an aqueous potassium iodide solution is generally used.

(41) Numeral 20 represents pulverized synthetic quartz particles having the particle diameter of 500 nm or less, which are mixed with ethanol and applied onto an electrode 15 made of platinum or the like and dried.

(42) Numeral 16 represents a transparent electrode made of FTO or the like, and numeral 17 represents a substrate made of glass or a resin. Numeral 18 represents a sealing material, and numeral 19 represents an external load.

(43) Among the ultraviolet light through infrared light entered from the transparent substrate 11 on the light incident side, the ultraviolet light through visible light enters the dye-sensitized porous titanium dioxide 10 to cause electric generation, and the ultraviolet light through infrared light which does not contribute to the electric generation enters the silicon dioxide 20 to cause electric generation.

(44) As mentioned above in connection with Embodiment 1, the silicon dioxide 20 causes electric generation using even light in the region from the visible light through the infrared light, where the titanium dioxide and sensitizing dye do not cause the electric generation.

(45) Thus, the solar cell according to Embodiment 3 can utilize the light in all the region from the ultraviolet light through the infrared light in electric generation.

(46) By the solar cell according to Embodiment 3, a short-circuit current of 285 μA and an open circuit voltage of 510 mV are obtained.

(47) FIG. 6 shows the voltage-current characteristics of the dye sensitized solar cell when varying the silicon dioxide and the voltage-current characteristics of the conventional dye sensitized solar cell.

(48) In FIG. 6, the voltage is taken as the abscissa, and the current is taken as the ordinate.

(49) In the graph, for example, indication “1.0E-03” means 1.0 mA.

(50) The characteristics are results of the measurement of a voltage and a current between the FTO electrodes using a solar simulator at the incident light energy of 1-Sun (i.e., 1 kW/m.sup.2) on the solar cell.

(51) FIG. 6 shows voltage-current characteristics curves of 6 samples A to E and G and a conventional dye sensitized solar cell F which is a comparative sample.

(52) Character A indicates a voltage-current characteristics curve obtained when using the synthetic quartz particles pulverized so as to have the particle diameter of 50 to 200 nm, in which the short-circuit current is 3,067 μA and the open circuit voltage is 660 mV.

(53) Character B indicates a voltage-current characteristics curve obtained when using the synthetic quartz particles having the particle diameter of 0.2 mm, in which the short-circuit current is 2,340 μA and the open circuit voltage is 680 mV.

(54) Character D indicates a voltage-current characteristics curve obtained when using fused quartz, in which the short-circuit current is 1, 293 μA and the open circuit voltage is 680 mV.

(55) Character C indicates a voltage-current characteristics curve obtained when using non-alkali glass, in which the short-circuit current is 1,850 μA and the open circuit voltage is 690 mV.

(56) Character E indicates a voltage-current characteristics curve obtained when using borosilicate glass, in which the short-circuit current is 930 μA and the open circuit voltage is 700 mV.

(57) Character F indicates a voltage-current characteristics curve of the conventional dye sensitized solar cell of FIG. 1(b), in which the short-circuit current is 733 μA and the open circuit voltage is 680 mV.

(58) Character G indicates a voltage-current characteristics curve obtained when using soda-lime glass, in which the short-circuit current is 626 μA and the open circuit voltage is 670 mV.

(59) As can be seen from these voltage-current characteristics curves, the dye sensitized solar cells using the silicon dioxide in A to E can extract the larger current, comparing to the conventional solar cell.

(60) Further, even in the case using soda-lime glass which generally seems to be poorer than the conventional solar cell, in some voltage region, the solar cell can extract the larger current than that achieved by the conventional solar cell.

Embodiment 4

(61) In Embodiment 1 shown in FIG. 3, the pulverized synthetic quartz particles to be used have the particle diameter as small as 500 nm or less, and, when the synthetic quartz particles applied onto the platinum electrode are dried and brought into contact with an electrolytic solution, the particles may be dispersed or suspended in the electrolytic solution as indicated by numeral 22 in FIG. 7.

(62) The current-voltage relationship of the silicon dioxide solar cell is not strongly affected even in such the state.

Embodiment 5

(63) In Embodiment 2 shown in FIG. 4, the pulverized synthetic quartz particles to be used have the particle diameter as small as 500 nm or less, and, when the synthetic quartz particles applied onto the platinum electrode are dried and brought into contact with an electrolytic solution, the particles may be dispersed or suspended in the electrolytic solution as indicated by numeral 22 in FIG. 8.

(64) The current-voltage relationship of the silicon dioxide solar cell having a porous titanium dioxide sintered material combined is not strongly affected even in such the state.

Embodiment 6

(65) In Embodiment 3 shown in FIG. 5, the pulverized synthetic quartz particles to be used have the particle diameter as small as 500 nm or less, and, when the synthetic quartz particles applied onto the platinum electrode are dried and brought into contact with an electrolytic solution, the particles may be dispersed or suspended in the electrolytic solution as indicated by numeral 22 in FIG. 9.

(66) The current-voltage relationship of the silicon dioxide solar cell having a dye-sensitized porous titanium dioxide sintered material combined is not strongly affected even in such the state.

Embodiment 7

(67) FIG. 10 shows the silicon dioxide solar cell according to Embodiment 6 which is obtained by improving Embodiment 5.

(68) In Embodiment 6, the pulverized synthetic quartz particles dispersed or suspended in the electrolytic solution have the particle diameter as small as 500 nm or less and are a poor conductor in essence, and therefore, may possibly penetrate into the pore portions of the porous titanium dioxide to inhibit the ability of the titanium dioxide to generate electricity.

(69) For preventing the occurrence of such the above accident, using a separating membrane 23 permeable only for the electrolyte, the electrolyte in which the silicon dioxide 22 is suspended and the electrolyte in which the silicon dioxide 22 is not suspended are separated from each other.

Embodiment 8

(70) FIG. 11 shows the silicon dioxide solar cell according to Embodiment 6 which is obtained by improving Embodiment 6.

(71) In Embodiment 6, the pulverized synthetic quartz particles dispersed or suspended in the electrolytic solution have the particle diameter as small as 500 nm or less and are a poor conductor in essence, and therefore, may possibly penetrate into the pore portions of the porous titanium dioxide to inhibit the ability of the titanium dioxide to generate electricity.

(72) For preventing the occurrence of such the above accident, using a separating membrane 23 permeable only for the electrolyte, the electrolyte in which the silicon dioxide 22 is suspended and the electrolyte in which the silicon dioxide 22 is not suspended are separated from each other.

Embodiment 9

(73) In the invention of the present application, with respect to the substrate, transparent conductive layer, counter electrode, electrolyte, and the like, various arrangements and materials other than those described in the aforementioned Embodiments can be used.

(74) Hereinbelow, the arrangements and materials usable as substitutes are described.

(75) [Substrate]

(76) In each of the Embodiments, with respect to the container containing therein the solar cell material and electrolyte, a light transmissive material is used on the light incident side, and a light transmissive or non-transmissive material is used on the side to which no incident light enters.

(77) As a light transmissive material, glass, plastics, amorphous silicon, or a polyester film can be used, and, as a light non-transmissive material, a metal plate of stainless steel, nickel, or the like is used.

(78) [Transparent Conductor]

(79) Almost all the glass and plastics used as a light transmissive material have no electrical conductivity, and, when using a material having no electrical conductivity, it is necessary to impart electrical conductivity to the material. As a light transmissive material having electrical conductivity, in addition to tin oxide, such as FTO or ITO, AZO (Al—ZN—O), a carbon material, such as carbon nanotubes or graphene, or a conductive PET film is used, and an electrode formed on a transparent material of glass, plastics, or the like is used. The transparent electrode is provided inside the solar cell.

(80) With respect to the side of the solar cell container opposite to the light incident side, when it is required to transmit the light, a transparent electrode made of FTO, ITO, carbon nanotubes, graphene, or the like formed on a transparent material of glass, a plastic, or the like is used, and, when it is not required to transmit the light, a metal plate forming thereon a conductor for extracting charges made of carbon nanotubes, graphene, or the like is used. The conductor for extracting charges is provided inside the solar cell.

(81) When conductive plastics is used as the plastics, the transparent conductor can be omitted.

(82) [Silicon Dioxide Particles]

(83) The halogen acid-treated crystalline synthetic quartz particles or amorphous glass particles are prepared as follows.

(84) Synthetic quartz which is crystalline silicon dioxide (SiO.sub.2), or glass particles of quartz glass, non-alkali glass, borosilicate glass, soda-lime, or the like, which is amorphous silicon dioxide, are immersed in an aqueous solution of hydrofluoric acid, and the resultant synthetic quartz particles or glass particles are washed with water and then dried, followed by pulverization.

(85) Hydrochloric acid is used as halogen acid other than hydrofluoric acid, but hydrofluoric acid is preferred.

(86) Alternatively, other halogen acid can be used.

(87) When the silicon dioxide particles are not treated with halogen acid, a sample of the silicon dioxide particles is pulverized so that the average particle diameter of the particles becomes several 10 nm.

(88) The treatment of the silicon dioxide particles with halogen acid can be performed after the pulverization but not before the pulverization.

(89) [Silicon Dioxide Layer]

(90) With respect to the silicon dioxide layer, there can be used a layer obtained by mixing synthetic quartz powder with ethanol together with platinum powder and subjecting the resultant mixture to calcination.

(91) The silicon dioxide particle calcinated material having the particle diameter of up to about 0.5 mm can be used.

(92) [Electrolyte]

(93) With respect to the electrolyte, as a supporting electrolyte, various types of electrolytes, e.g., cations, such as lithium ions, or anions, such as chloride ions, are used, and, as oxidation-reduction pair present in the electrolyte, an oxidation-reduction pair, such as an iodine-iodine compound or a bromine-bromine compound, is used.

(94) 0.4 mol of 1-ethyl-3-methylimidazolium iodide, 0.4 mol of tetrabutylammonium iodide, 0.2 mol of 4-tert-butylpyridine, and 0.1 mol of guanidine isothiocyanate are dissolved in propylene carbonate liquid as a solvent to prepare an electrolyte.

(95) When the concentration of halogen molecules in the electrolyte is 0.0004 mol/L or less, the electrolyte is almost colorless and transparent in the visible light region.

(96) 0.5 mol of lithium iodide (LiI) and 0.05 mol of metallic iodine (I.sub.2) are dissolved in methoxypropionitrile, and thickener is added to the resultant solution, and further 4-tert-butylpyridine is added thereto for improving the open electromotive ability and fill factor.

(97) When the composite glass plate needs neither be colorless nor transparent, colored electrolytic solution, such as the iodine electrolytic solution, can be used.

(98) Organic acid, such as acetic acid or citric acid, can be used as the colorless electrolyte.

(99) [Sensitizing Dye]

(100) By using sensitizing dye, the titanium dioxide solar cell can utilize light in the ultraviolet light and visible light region in electric generation. When the silicon dioxide solar cell satisfactorily causes electric generation using the light in the visible light region, it is not necessary to use expensive sensitizing dye having a short life.

(101) With respect to the sensitizing dye other than the ruthenium complex dye, cobalt complex dye, porphyrin, cyanine, merocyanine, phthalocyanine, coumarin, riboflavin, xanthene, triphenylmethane, azo, quinone, C60 derivative, BTS (styryl benzothiazolium propylsulfonate), indoline, or dye derived from a plant, such as hibiscus or American cherry, can be used, and, by choosing from the dye having different electric generation properties, the light usable in the electric generation can be appropriately selected.

(102) [Counter Electrode]

(103) With respect to the semiconductor layer as a counter electrode, other than the zinc oxide (ZnO), titanium dioxide (TiO.sub.2), copper oxide (CuO), magnesium oxide (MgO), strontium titanate (SrTiO.sub.3), carbon nitride, graphene, or the like can be used.

(104) [Surface on the Light Incident Side]

(105) In all the Embodiments described above, the silicon dioxide calcinated material is disposed on the side to which no incident light enters. There is no absolute reason for this arrangement, and therefore the silicon dioxide calcinated material can be disposed on the side to which the incident light enters.

INDUSTRIAL APPLICABILITY

(106) According to the invention of the present application, combining further a silicon dioxide solar cell in a tandem configuration in a titanium dioxide solar cell container, there can be obtained a solar cell which is advantageous in that it can utilize light in all the region from the ultraviolet light through the infrared light in electric generation.

REFERENCE NUMERALS

(107) 1, 7, 11, 17: Substrate 2, 6, 12, 16: Transparent conductive layer 3: Porous titanium dioxide sintered material 4, 14: Electrolyte 5, 15: Counter electrode 8, 18: Sealing material 9: External load 10: Dye-sensitized porous titanium dioxide sintered material 20: silicon dioxide particles compact 22: Silicon dioxide particles