solar cells

Abstract

To provide solar cells that can suppress degradation. [Solution] A solar cell 1 comprising a crystalline silicon substrate 11, a first semiconductor layer 12 laminated on the back side of the crystalline silicon substrate 11, a second semiconductor layer 13 laminated on the front side of the crystalline silicon substrate 11, a back electrode layer 14 laminated on the back side of the first semiconductor layer 12, an intermediate layer 15 laminated on the front side of the second semiconductor layer 13, a third semiconductor layer 16 laminated on the front side of the intermediate layer 15, a perovskite photoelectric conversion layer 17 laminated on the front side of the third semiconductor layer 16, a fourth semiconductor layer 18 laminated on the front side of the perovskite photoelectric conversion layer 17, and a surface electrode layer 19 laminated on the front side of the fourth semiconductor layer 18, wherein the perovskite photoelectric conversion layer 17 extends to cover the end face of the second semiconductor layer 13.

Description

Technical Field

[0001] The present invention relates to a solar battery cell.

Background Art

[0002] The use of solar batteries as an energy source with low environmental impact is expanding. When solar batteries are installed in various devices, vehicles, buildings, etc., the installable area is limited, so the photoelectric conversion efficiency of solar battery cells can be important. As solar battery cells with high photoelectric conversion efficiency, development of tandem-type solar battery cells formed by stacking two types of photoelectric conversion layers having different absorption wavelengths is progressing. As an example, a monolithic tandem-type solar battery cell is proposed in which a perovskite photoelectric conversion body having a perovskite photoelectric conversion layer excellent in photoelectric conversion efficiency in a short wavelength range is directly laminated on the surface of a crystalline silicon solar battery having a wide absorption wavelength range (see, for example, Patent Document 1).

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] Solar battery cells may deteriorate due to contact with moisture or the like. In particular, when moisture or the like enters from an end face to an interface forming a PN junction, the photoelectric conversion efficiency of the solar battery cell may decrease. Accordingly, an object of the present invention is to provide a solar battery cell capable of suppressing deterioration.

Means for Solving the Problem

[0005] (1) A solar cell according to one aspect of the present invention comprises a crystalline silicon substrate, a first semiconductor layer laminated on the back side of the crystalline silicon substrate, a second semiconductor layer laminated on the front side of the crystalline silicon substrate, a back electrode layer laminated on the back side of the first semiconductor layer, an intermediate layer laminated on the front side of the second semiconductor layer, a third semiconductor layer laminated on the front side of the intermediate layer, a perovskite photoelectric conversion layer laminated on the front side of the third semiconductor layer, a fourth semiconductor layer laminated on the front side of the perovskite photoelectric conversion layer, and a surface electrode layer laminated on the front side of the fourth semiconductor layer, wherein the perovskite photoelectric conversion layer extends to cover the end face of the second semiconductor layer.

[0006] (2) In the solar cell of (1), the perovskite photoelectric conversion layer may further extend to cover the end face of the crystalline silicon substrate.

[0007] (3) In the solar cell described in (1) and (2), the perovskite photoelectric conversion layer may further extend to the back side of the outer edge of the back electrode layer.

[0008] (4) In the solar cell according to (1) to (3), the third semiconductor layer may extend so as to cover the end face of the second semiconductor layer.

[0009] (5) In the solar cell described in (1) to (4), the intermediate layer does not need to be laminated on the outer edge of the second semiconductor layer. [Effects of the Invention]

[0010] The solar cell according to the present invention can suppress degradation. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of a solar cell according to the first embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of a solar cell according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions of various components in the drawings have been adjusted for ease of viewing. Furthermore, in embodiments described later, components similar to those described earlier are denoted by the same reference numerals, and redundant explanations may be omitted.

[0013] [First Embodiment] Figure 1 is a schematic cross-sectional view of a solar cell 1 according to a first embodiment of the present invention. The solar cell 1 comprises a crystalline silicon substrate 11, a first semiconductor layer 12, a second semiconductor layer 13, a back electrode layer 14, an intermediate layer 15, a third semiconductor layer 16, a perovskite photoelectric conversion layer 17, a fourth semiconductor layer 18, and a front electrode layer 19. In the solar cell 1, the crystalline silicon substrate 11, the first semiconductor layer 12, and the second semiconductor layer 13 constitute a first photoelectric converter, and the third semiconductor layer 16, the perovskite photoelectric conversion layer 17, and the fourth semiconductor layer 18 constitute a second photoelectric converter. In other words, the solar cell 1 is a monolithic tandem type solar cell.

[0014] The crystalline silicon substrate 11 absorbs incident light and generates photocarriers (electrons and holes). The crystalline silicon substrate 11 also functions as a substrate for supporting other components. The crystalline silicon substrate 11 can be formed from a crystalline silicon material such as single-crystal silicon or polycrystalline silicon. The crystalline silicon substrate 11 can be, for example, an n-type semiconductor substrate doped with an n-type dopant in a crystalline silicon material. An example of an n-type dopant is phosphorus (P). Alternatively, the crystalline silicon substrate 11 may be a p-type semiconductor substrate doped with a p-type dopant in a crystalline silicon material. An example of a p-type dopant is boron (B). By using crystalline silicon as the material for the crystalline silicon substrate 11, the dark current is relatively small, and relatively high output (stable efficiency regardless of illuminance) can be obtained even when the intensity of incident light is low. The crystalline silicon substrate 11 may have a pyramidal, fine uneven structure called a texture structure on its main surface in order to improve the incidence rate of light.

[0015] The first semiconductor layer 12 is laminated over the entire back surface of the crystalline silicon substrate 11. The first semiconductor layer 12 is a semiconductor layer having a first conductivity type and selectively extracts only one polarity of the photocarriers generated in the crystalline silicon substrate 11. The first semiconductor layer 12 may be formed from a thin film of amorphous silicon and may contain the same dopant as the crystalline silicon substrate 11, but at a higher concentration than the crystalline silicon substrate 11. In this embodiment, the first semiconductor layer 12 is formed from a p-type semiconductor to extract electrons. The first semiconductor layer 12 may be formed by a film deposition technique such as CVD or PVD.

[0016] The second semiconductor layer 13 is laminated over the entire surface side of the crystalline silicon substrate 11. The second semiconductor layer 13 is a semiconductor layer having a second conductivity type different from that of the first semiconductor layer 12, and selectively extracts carriers having a polarity different from that of the first semiconductor layer 12. The second semiconductor layer 13 may be formed from an amorphous silicon thin film with a different dopant type from that of the first semiconductor layer 12. In this embodiment, the second semiconductor layer 13 is formed of an n-type semiconductor to extract holes. Similarly to the first semiconductor layer 12, the second semiconductor layer 13 may be formed by a film formation technique such as CVD, PVD, or the like.

[0017] The back electrode layer 14 is a conductor for leading out charges extracted by the first semiconductor layer 12 to the outside. The back electrode layer 14 may be formed of metal, a metal-based conductive paste, transparent conductive oxide (TCO: Transparent Conductive Oxide), or the like, and may have a configuration including a plurality of these materials. In particular, in order to improve adhesion to the second semiconductor layer 13, the back electrode layer 14 preferably has a transparent conductive oxide layer on a surface in contact with the second semiconductor layer 13. The transparent conductive oxide can be formed of, for example, indium oxide, tin oxide, zinc oxide, titanium oxide, composite oxides thereof, or the like. Among these, it is preferably formed of ITO (Indium Tin Oxide) obtained by adding tin to indium oxide. The intermediate layer 15 can be formed by a method such as CVD, PVD, printing, coating, plating, or the like depending on its material.

[0018] The intermediate layer 15 is laminated on the surface side of the second semiconductor layer 13. The intermediate layer 15 has conductivity, is interposed between the first semiconductor layer 12 and the third semiconductor layer 16, and electrically connects the second semiconductor layer 13 and the third semiconductor layer 16. The intermediate layer 15 can be formed of a transparent conductive oxide, for example, indium oxide, tin oxide, zinc oxide, titanium oxide, composite oxides thereof, or the like. Among these, it is preferably formed of ITO obtained by adding tin to indium oxide. The intermediate layer 15 can be formed by a film formation technique such as CVD, PVD, or the like.

[0019] The third semiconductor layer 16 is laminated over the entire surface side of the intermediate layer 15, and extracts charges from the perovskite photoelectric conversion layer 17 that have a different polarity from the charges extracted by the second semiconductor layer 13 from the crystalline silicon substrate 11. In this embodiment, the third semiconductor layer 16 is a hole transport layer (HTL) that extracts holes. The main material of the third semiconductor layer 16, which is a hole transport layer, is preferably a material whose highest occupied orbital is close to the valence band of the perovskite compound that performs photoelectric conversion, in order to facilitate hole transfer, and is also preferably a material whose lowest unoccupied orbital is smaller than the conduction band in order to block electrons. Specific main materials for the third semiconductor layer 16 include metal oxides such as nickel oxide (NiO) and copper oxide (Cu2O), organic materials that form self-assembled monolayers (SAMs) such as 2PACz ([2-(9H-Carbazol-9-yl)ethyl]phosphonic Acid), MeO-2PACz ([2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic Acid), Me-4PACz ([4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid), and DMAcPA ((4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid), such as PTAA (poly(triaryl amine)) and Spiro-MeOTAD ([2,2',7,7'-Tetrakis(N,N Examples of organic materials include [-di-p-methoxyphenylamino)-9,9'-spirobifluorene]). The third semiconductor layer 16 may also have a multilayer structure. The third semiconductor layer 16 can be formed by film deposition techniques such as CVD or PVD in the case of a metal oxide, or by methods such as coating in the case of an organic material.

[0020] The perovskite photoelectric conversion layer 17 is laminated over the entire surface side of the third semiconductor layer 16, contains a perovskite compound that performs photoelectric conversion, absorbs incident light and generates photocarriers. The perovskite photoelectric conversion layer 17 extends to cover the end face of the second semiconductor layer 13. Since the perovskite photoelectric conversion layer 17 has a property of easily trapping moisture, by being disposed to cover the end face of the second semiconductor layer 13, it can prevent moisture from intruding into the interface between the crystalline silicon substrate 11 and the second semiconductor layer 13. It is preferable that the perovskite photoelectric conversion layer 17 further extends to cover the end face of the crystalline silicon substrate in order to prevent moisture from intruding into the interface between the crystalline silicon substrate 11 and the first semiconductor layer 12, and it is more preferable that the perovskite photoelectric conversion layer 17 further extends to cover the end face of the first semiconductor layer 12 in order to prevent moisture from intruding into the interface between the first semiconductor layer 12 and the back electrode layer 14.

[0021] As the perovskite compound contained in the perovskite photoelectric conversion layer 17, a compound represented by ABX₃ can be used, which comprises an organic atomic group A containing at least one of monovalent organic ammonium ions and amidinium-based ions, a metal atom B that generates a divalent metal ion, and a halogen atom X containing at least one of iodide ion I⁻, bromide ion Br⁻, chloride ion Cl⁻ and fluoride ion F⁻. Further, the perovskite photoelectric conversion layer 17 can be formed by, for example, a method such as a sol-gel method in which a perovskite compound is synthesized in a liquid-phase coating film, or a coating method in which a solution containing a pre-synthesized perovskite compound is applied. Further, the perovskite photoelectric conversion layer 17 can also be formed by, for example, sequentially forming films of a material containing a metal halide BX and a material containing an organic atomic group halide AX, and reacting the thin films of these materials at a reaction temperature.

[0022] Examples of organic atomic group A include methylammonium MA (CH3NH3) and formamidinium FA (CH3N2). Substitution of part or all of organic atomic group A with alkali metal Am is also being considered, and such perovskite compounds are not excluded from the present invention. Examples of alkali metal Am include potassium K, cesium Cs, and rubidium Rb. Among these, cesium Cs and rubidium Rb are preferred when durability and water resistance of the solar cell 1 are important, with cesium Cs being particularly preferred from the viewpoint of cost and availability. Examples of metal atom B include lead Pb and tin Sn. When power generation efficiency of the solar cell 1 is important, it is preferable that metal atom B is mainly lead. The lower limit of the lead content in metal atom B is preferably 50% by weight, more preferably 80% by weight, and even more preferably 90% by weight, in order to achieve the desired performance. On the other hand, when the environmental impact of lead is important, it is preferable that metal atom B is mainly tin Sn. The lower limit of the proportion of tin in metal atom B is preferably 50% by weight, more preferably 80% by weight, and particularly preferably 90% by weight, in order to achieve the desired performance. As halogen atom X, at least one of iodide I, bromide Br, and chloride Cl is preferred.

[0023] Specifically, preferred perovskite compounds include, for example, methylammonium lead halides (MAPbX3) such as MAPbI3, MAPbBr3, and MAPbCl3, and formamidinium lead halides (FAPbX3) such as FAPbI3, FAPbBr3, and FAPbCl3. Note that the halogen atom X may contain multiple types, and the organic atomic group A may contain both methylammonium and formamidinium. y MA 1-y PbX3 may also be used. Furthermore, if it contains the alkali metal Am, Am y FA z MA 1-y-z PbI X AmyFA 1-y PbI XExamples include the following. Am may be a single type of Cs, Rb, or K, or it may contain multiple types (where y and z are any positive integers).

[0024] The fourth semiconductor layer 18 is laminated over the entire surface side of the perovskite photoelectric conversion layer 17 and extracts charges with a polarity different from that of the third semiconductor layer 16 from the perovskite photoelectric conversion layer 17. In this embodiment, the fourth semiconductor layer 18 is an electron transport layer (ETL) that extracts electrons. The fourth semiconductor layer 18, which is an electron transport layer, can be formed from a material mainly composed of, for example, fullerene. Examples of fullerenes include C60, C70, their hydrides, oxides, metal complexes, alkyl groups, etc., derivatives to which such as PCBM ([6,6]-Phenyl-C61-Butyric Acid Methyl Ester) can be added. Alternatively, the fourth semiconductor layer 18 may be formed from an organic material such as pasocuproine (BCP), or from an inorganic oxide such as lithium fluoride (LiF), tin oxide (SnO2), aluminum-doped zinc oxide (ZnO), or titanium oxide (TiO2). The inorganic oxide forming the fourth semiconductor layer 18 can be doped with another metallic material.

[0025] The surface electrode layer 19 is an electrode paired with the back electrode layer 14 and is laminated over the entire surface side of the fourth semiconductor layer 18. The surface electrode layer 19 can be formed from a transparent conductive oxide, such as indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof, and among these, it is preferable to form it from ITO, which is indium oxide with added tin. The surface electrode layer 19 can be formed by film deposition techniques such as CVD and PVD.

[0026] As described above, the solar cell 1 according to this embodiment can prevent deterioration of the second semiconductor layer 13 due to contact with moisture, etc., by covering at least the end face of the second semiconductor layer 13 with the perovskite photoelectric conversion layer 17, thereby suppressing a decrease in photoelectric conversion efficiency over a long period of time.

[0027] [Second Embodiment] Figure 2 is a schematic cross-sectional view of a solar cell 1A according to a second embodiment of the present invention. The solar cell 1A comprises a crystalline silicon substrate 11, a first semiconductor layer 12, a second semiconductor layer 13, a back electrode layer 14, an intermediate layer 15A, a third semiconductor layer 16A, a perovskite photoelectric conversion layer 17A, a fourth semiconductor layer 18, and a front electrode layer 19.

[0028] In this embodiment, the intermediate layer 15A is not laminated on the outer edge of the second semiconductor layer 13. That is, the intermediate layer 15A is recessed inward in a plan view from the outer edge of the second semiconductor layer 13. This prevents wiring materials connecting the solar cell 1A to the outside from coming into contact with the intermediate layer 15A and causing a short circuit. When this configuration is adopted, the surface side of the outer edge of the second semiconductor layer 13 is not covered with the moisture-resistant intermediate layer 15A, so the effect of the present invention in suppressing degradation by covering it with the perovskite photoelectric conversion layer 17A becomes more pronounced.

[0029] In this embodiment, the third semiconductor layer 16A extends to cover at least the end face of the second semiconductor layer 13. This further suppresses the degradation of the second semiconductor layer 13 due to moisture and improves the adhesion of the perovskite photoelectric conversion layer 17A to the end face of the second semiconductor layer 13, etc. The third semiconductor layer 16A may extend to cover the end faces of the crystalline silicon substrate 11 and the first semiconductor layer 12, or, as in this embodiment, it may extend to the back side of the outer edge of the back electrode layer 14.

[0030] In this embodiment, the perovskite photoelectric conversion layer 17A extends to the back side of the outer edge of the back electrode layer 14. This prevents moisture from entering the interfaces of each layer, thereby more reliably suppressing the degradation of the solar cell 1A. Furthermore, by having the perovskite photoelectric conversion layer 17A wrap around to the back side of the back electrode layer 14, it becomes easier to control the thickness of the perovskite photoelectric conversion layer 17A at the end face, thereby improving the productivity of the solar cell 1A. Note that since the perovskite photoelectric conversion layer 17A can hardly conduct current in the planar direction, a short circuit will not occur even if the perovskite photoelectric conversion layer 17A comes into contact with the back electrode layer 14.

[0031] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and variations are possible. The solar cell according to the present invention may have a multilayer structure for each layer, and may further include layers that perform additional functions. For example, the solar cell according to the present invention may be provided with a passivation layer that suppresses the recombination of photocarriers at the interface of the crystalline silicon substrate or the perovskite photoelectric conversion layer, a junction layer interposed to improve the adhesion of each layer, and so on. Furthermore, the solar cell according to the present invention may also include further configurations such as finger electrodes for guiding current from the surface electrode layer to the outside. [Explanation of symbols]

[0032] 1.1A solar cell 11. Crystalline silicon substrate 12. First Semiconductor Layer 13. Second Semiconductor Layer 14 Back electrode layer 15,15A middle layer 16,16A Third semiconductor layer 17,17A Perovskite Photoelectric Conversion Layer 18. Fourth Semiconductor Layer 19 Surface electrode layer

Claims

1. Crystalline silicon substrate and A first semiconductor layer is laminated on the back side of the crystalline silicon substrate, A second semiconductor layer is laminated on the surface side of the crystalline silicon substrate, A back electrode layer stacked on the back side of the first semiconductor layer, An intermediate layer stacked on the surface side of the second semiconductor layer, A third semiconductor layer is stacked on the surface side of the intermediate layer, A perovskite photoelectric conversion layer is stacked on the surface side of the third semiconductor layer, A fourth semiconductor layer is stacked on the surface side of the perovskite photoelectric conversion layer, A surface electrode layer stacked on the surface side of the fourth semiconductor layer, Equipped with, The perovskite photoelectric conversion layer extends to cover the end face of the second semiconductor layer, forming a solar cell.

2. The solar cell according to claim 1, wherein the perovskite photoelectric conversion layer further extends to cover the end face of the crystalline silicon substrate.

3. The solar cell according to claim 1 or 2, wherein the perovskite photoelectric conversion layer further extends to the back side of the outer edge of the back electrode layer.

4. The solar cell according to claim 1 or 2, wherein the third semiconductor layer extends to cover the end face of the second semiconductor layer.

5. The solar cell according to claim 1 or 2, wherein the intermediate layer is not laminated on the outer edge of the second semiconductor layer.

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