Solar cell structure

Abstract

The invention provides a solar cell structure. The solar cell structure includes: a back contact cell having a back electrode on a back surface thereof; the first perovskite cell is located on the side, away from the back electrode, of the back contact cell, and the surface of the side, away from the back contact cell, of the first perovskite cell is provided with an upper electrode; and the second perovskite cell is located between the back contact cell and the first perovskite cell, and the band gap of the perovskite absorption layer of the first perovskite cell is different from the band gap of the perovskite absorption layer of the second perovskite cell. According to the invention, the utilization rate of solar photons is expanded, so that the limit photoelectric conversion efficiency of the solar cell structure is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a solar cell structure. Background Art

[0002] Photovoltaic power generation technology converts solar energy into electrical energy based on the photovoltaic effect, and the efficiency of photoelectric conversion has been significantly improved in the past 10 years. Crystalline silicon cells have high efficiency, good stability, and mature manufacturing processes, and they dominate the photovoltaic market. However, as the conversion efficiency of existing crystalline silicon cells is approaching the limit efficiency of 29.4%, considering the sustainable development of photovoltaic technology in the future, researchers are focusing on potential emerging photovoltaic technologies with different application directions, higher efficiency and lower cost, such as stacked cells.

[0003] Among them, the common stacked cells have two structures: 2-terminal (2-T) and 4-terminal (4-T). The 2-T cell structure uses an intermediate layer (common materials are TCO, heavily doped nc-Si:H and nc-SiOx:H) to connect two sub-cells. This structure needs to consider the current matching problem of the top and bottom cells; while the 4-T cell structure forms a stacked cell by simple stacking. Therefore, the top cell and the bottom cell retain their positive and negative electrodes respectively, forming a 4-terminal structure. However, the 4-T stacked cell needs to solve the interconnection problem between the surfaces of the two individual sub-cells. Therefore, the common 2-terminal (2-T) and 4-terminal (4-T) stacked cells mentioned above each have their own disadvantages.

[0004] Therefore, a new solar cell structure is urgently needed to improve the photoelectric conversion efficiency of solar cells. Summary of the invention

[0005] The main purpose of the present invention is to provide a solar cell structure to solve the problem of low photoelectric conversion efficiency of solar cells in the prior art.

[0006] In order to achieve the above-mentioned purpose, a solar cell structure is provided, comprising: a back contact cell, wherein the back surface of the back contact cell has a back electrode; a first perovskite cell, located on a side of the back contact cell away from the back electrode, and the first perovskite cell has an upper electrode on a surface on a side away from the back contact cell; a second perovskite cell, located between the back contact cell and the first perovskite cell, and the band gap of the perovskite absorption layer of the first perovskite cell is different from the band gap of the perovskite absorption layer of the second perovskite cell.

[0007] Furthermore, the band gap width of the perovskite absorption layer of the first perovskite cell is greater than the band gap width of the perovskite absorption layer of the second perovskite cell.

[0008] Furthermore, the above-mentioned back contact cell includes an interdigitated back contact heterojunction cell.

[0009] Furthermore, the solar cell structure further includes: a first conductive layer located between the back contact cell and the second perovskite cell.

[0010] Furthermore, the solar cell structure further includes: a second conductive layer located between the first perovskite cell and the second perovskite cell, wherein the second conductive layer includes a first transparent conductive oxide layer and a first transition metal oxide layer which are stacked.

[0011] Furthermore, the above-mentioned back contact battery includes a first intrinsic amorphous silicon passivation layer, a silicon substrate, a second intrinsic amorphous silicon passivation layer and a doping layer which are stacked in sequence, the above-mentioned first intrinsic amorphous silicon passivation layer is connected in series with the above-mentioned second perovskite battery, and the above-mentioned doping layer has the above-mentioned back electrode on the surface of the side away from the above-mentioned second intrinsic amorphous silicon passivation layer.

[0012] Furthermore, the back contact battery also includes a groove area extending from the back surface to the silicon substrate, and the doping layer includes an N+ doping area and a P+ doping area, and the N+ doping area and the P+ doping area are located on both sides of the groove area.

[0013] Furthermore, the back electrode comprises a second transparent conductive oxide layer and a metal layer, and the metal layer is located on a side of the second transparent conductive oxide layer away from the second perovskite cell.

[0014] Furthermore, the first perovskite cell comprises an electron transport layer, a perovskite absorption layer, a hole transport layer and a reflective layer stacked in sequence, the electron transport layer is connected in series with the second perovskite cell, and the upper electrode is located on an exposed surface of the reflective layer.

[0015] Furthermore, a buffer layer is provided between the reflective layer and the hole transport layer, and the buffer layer includes a third transparent metal conductive oxide layer and a second transition metal oxide layer.

[0016] The technical solution of the present invention is applied to provide a solar cell structure, which includes a back contact cell with a back electrode, a first perovskite cell with an upper electrode, and a second perovskite cell. Since the first perovskite cell is located on a side of the back contact cell away from the back electrode, the second perovskite cell is also located between the back contact cell and the first perovskite cell, and the upper electrode is located on a side of the first perovskite cell away from the second perovskite cell, the solar cell structure only includes two electrodes. Therefore, compared with a stacked solar cell formed by interconnecting multiple independent sub-cells, the solar cell structure of the present application avoids the interconnection problem between two adjacent independent sub-cells; and further, the solar cell structure simultaneously has a crystalline silicon cell (back contact cell) and a perovskite cell (first perovskite cell). Perovskite cell and the second perovskite cell), since the band gap of the perovskite material is larger than the band gap of the crystalline silicon material, the back contact cell as a low band gap sub-cell broadens the utilization rate of solar photons, and the first perovskite cell and the second perovskite cell as high band gap sub-cells reduce the thermal energy loss in the relaxation process after the semiconductor material in the solar cell structure captures photons and the electron transition, so compared with the single junction cell, the solar cell structure of the present application has a higher ultimate photoelectric conversion efficiency, and further, the band gap of the perovskite absorption layer of the first perovskite cell in the present application is different from the band gap of the perovskite absorption layer of the second perovskite cell, so that the first perovskite cell or the second perovskite cell with a lower band gap can also be used to broaden the utilization rate of solar photons, thereby further improving the ultimate photoelectric conversion efficiency of the solar cell structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 A schematic cross-sectional structure diagram of a solar cell structure according to an embodiment of the present invention is shown;

[0019] Figure 2 A schematic cross-sectional structure diagram of a solar cell structure according to another embodiment of the present invention is shown.

[0020] The above drawings include the following reference numerals:

[0021] 10. Back contact cell; 20. Second perovskite cell; 30. First perovskite cell; 40. First conductive layer; 50. Second conductive layer. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] As mentioned in the background technology, since the conversion efficiency of existing crystalline silicon cells has reached its limit, considering the sustainable development of photovoltaic technology, researchers have proposed a stacked cell structure, such as a 2-terminal (2-T) solar cell and a 4-terminal (4-T) solar cell. However, the existing 2-terminal (2-T) solar cell and 4-terminal (4-T) solar cell are both composed of multiple sub-cell structures stacked on each other. When multiple sub-cells are connected, there will be current matching or interconnection problems between different sub-cells. Therefore, in order to improve the conversion efficiency of solar cells, a new solar cell structure is urgently needed.

[0026] According to one aspect of the present application, the inventor of the present application provides a solar cell structure, such as Figure 1 As shown, the solar cell structure includes: a back contact cell 10, wherein the back surface of the back contact cell 10 has a back electrode; a first perovskite cell 30, located on a side of the back contact cell 10 away from the back electrode, and the first perovskite cell 30 has an upper electrode on a side surface away from the back contact cell 10; a second perovskite cell 20, located between the back contact cell 10 and the first perovskite cell 30, and the band gap of the perovskite absorption layer of the first perovskite cell 30 is different from the band gap of the perovskite absorption layer of the second perovskite cell.

[0027] Specifically, the back-contact cell 10 has no metal electrode on the light-receiving surface (front surface) of the cell, which can completely eliminate the optical loss on the front side and increase the short-circuit current of the cell. All electrodes are distributed in a cross shape on the back surface of the cell. The back-contact cell 10 in the present application can be used as the bottom cell of the above-mentioned solar cell structure, and since the back surface of the back-contact cell 10 has a back electrode, the back electrode is the back electrode of the above-mentioned solar cell structure.

[0028] Specifically, the above-mentioned back contact cell 10 may include but is not limited to an interdigitated back contact cell 10 (IBC), an interdigitated back contact heterojunction cell (HBC), a full back contact crystalline silicon cell (ABC), a composite passivated back contact cell 10 (HPBC), etc.

[0029] Specifically, a perovskite cell is a solar cell that uses a perovskite-type organic metal halide semiconductor as a light-absorbing material. Since the light-absorbing material has a strong light-absorbing ability, the conversion efficiency of the solar cell is improved. Furthermore, the above-mentioned perovskite cell can include an organic perovskite cell, an inorganic perovskite cell, and a hybrid perovskite cell, depending on its structure and material. Among them, the above-mentioned organic perovskite cell uses an organic substance as an electron transport material, the above-mentioned inorganic perovskite cell uses an inorganic substance as an electron transport material, and the above-mentioned hybrid perovskite cell uses both organic and inorganic substances as electron transport materials.

[0030] Specifically, the above-mentioned solar cell of the present application is at least a triple-junction tandem solar cell structure, and the sub-cells in the triple-junction tandem solar cell structure may include a back contact cell 10 and a perovskite cell, wherein the perovskite cell includes a first perovskite cell 30 and a second perovskite cell 20, the back contact cell 10 serves as the bottom cell of the triple-junction tandem solar cell structure, the first perovskite cell 30 serves as the top cell of the triple-junction tandem solar cell structure, and the second perovskite cell 20 serves as the middle cell of the triple-junction tandem solar cell structure. Therefore, the back contact cell 10, the second perovskite cell 20 and the first perovskite cell 30 are sequentially stacked, wherein the back contact cell 10 has a front surface and a back surface, the back surface is a surface away from the second perovskite cell 20, and a back electrode is arranged on the back surface, which serves as the back electrode of the triple-junction tandem solar cell structure, and the first perovskite cell 30 has a side surface away from the back contact cell 10, and an upper electrode is provided on the surface, which is the upper electrode of the triple-junction tandem solar cell structure.

[0031] Through the present application, since a solar cell structure including a back contact cell 10 with a back electrode, a first perovskite cell 30 with an upper electrode and a second perovskite cell 20 is adopted, and the above-mentioned first perovskite cell 30 is located on the side of the back contact cell 10 away from the back electrode, the second perovskite cell 20 is also located between the back contact cell 10 and the first perovskite cell 30, and the above-mentioned upper electrode is located on the side of the first perovskite cell 30 away from the second perovskite cell 20, the solar cell structure only includes two electrodes, so that relative to a stacked solar cell formed by interconnecting multiple independent sub-cells, the above-mentioned solar cell structure of the present application avoids the interconnection problem between two adjacent independent sub-cells; and further, the solar cell structure simultaneously has a crystalline silicon cell (back contact cell 10) and a perovskite cell (first perovskite cell 30 and the second perovskite cell 20), since the band gap of the perovskite material is larger than the band gap of the crystalline silicon material, the back contact cell 10 as a low band gap sub-cell broadens the utilization rate of solar photons, and the first perovskite cell 30 and the second perovskite cell 20 as high band gap sub-cells reduce the heat energy loss in the relaxation process after the semiconductor material in the solar cell structure captures photons and the electron transition, so compared with the single junction cell, the solar cell structure of the present application has a higher ultimate photoelectric conversion efficiency, and further, the band gap of the perovskite absorption layer of the first perovskite cell 30 in the present application is different from the band gap of the perovskite absorption layer of the second perovskite cell 20, so that the first perovskite cell 30 or the second perovskite cell 20 with a lower band gap can also be used to broaden the utilization rate of solar photons, thereby further improving the ultimate photoelectric conversion efficiency of the solar cell structure.

[0032] In some optional embodiments, the band gap width of the perovskite absorption layer of the first perovskite cell 30 is greater than the band gap width of the perovskite absorption layer of the second perovskite cell 20 .

[0033] In the above-mentioned embodiment, since the first perovskite cell 30 in the present application is the first to be exposed to sunlight relative to the second perovskite cell 20 and the back contact cell 10, in order to absorb more sunlight, the heat energy loss in the relaxation process after the semiconductor material in the solar cell structure captures photons and the electron transition is reduced, so that the first perovskite cell 30 in the solar cell structure that is first exposed to sunlight can absorb the shortest-wave light in the sunlight, and allows light with longer wavelengths to be transmitted from the first perovskite cell 30 so that the second perovskite cell 20 and the back contact cell 10 can absorb and utilize it. Therefore, the inventor of the present application adjusted the band gap width of the perovskite absorption layer of the first perovskite cell 30 and the band gap width of the perovskite absorption layer of the second perovskite cell 20, so that the band gap width of the perovskite absorption layer of the first perovskite cell 30 for absorbing the shortest wavelength light is greater than the band gap width of the perovskite absorption layer of the second perovskite cell 20 for absorbing shorter wavelength light, thereby maximizing the use of sunlight to improve the photoelectric conversion efficiency of the solar cell structure.

[0034] In some optional embodiments, the back contact cell 10 comprises an interdigitated back contact heterojunction cell.

[0035] Specifically, the interdigitated back contact heterojunction cell (HBC) is obtained by combining the interdigitated back contact cell 10 (IBC) with a heterojunction solar cell (HJT), wherein the interdigitated back contact heterojunction cell (HBC) may include a back electrode, a transparent metal oxide film, a doping layer (a cross-arranged P-type amorphous silicon doped film pa-Si:H and an N-type amorphous silicon doped film na-Si:H), an intrinsic amorphous silicon film ia-Si:H, a silicon substrate, an intrinsic amorphous silicon film ia-Si:H and a P-type amorphous silicon film pa-Si:H, which are stacked in sequence. In the above embodiment, since the P-type amorphous silicon doped film pa-Si:H and the N-type amorphous silicon doped film na-Si:H are hydrogenated amorphous silicon layers, the hydrogenated amorphous silicon layers can serve as double-sided passivation layers of the back contact cell 10, and can form a local a-Si / c-Si heterojunction structure on the back of the back contact cell 10. Based on high-quality amorphous silicon passivation, the solar cell of the present application obtains a high open circuit voltage (Voc).

[0036] Optionally, in the process of forming the back contact cell 10, the front side of the silicon substrate may be polished first, and the back side of the silicon substrate may be textured, and then hydrogenated amorphous silicon (P-type amorphous silicon doped film pa-Si:H and N-type amorphous silicon doped film na-Si:H) and nanocrystalline silicon layer (intrinsic amorphous silicon film ia-Si:H) may be deposited by RF-PECVD. A transparent metal oxide film (e.g., an ITO layer) may be sputtered by RF, and then a back electrode (e.g., an Ag layer) may be formed on the surface of the transparent metal oxide film by thermal evaporation deposition.

[0037] Since the back contact cell 10 is a crystalline silicon cell, when the second perovskite cell 20 is connected in series with the back contact cell 10, the conductivity between the back contact cell 10 and the second perovskite cell 20 is poor or there is a problem of non-radiative recombination loss of photogenerated carriers at the contact interface between the back contact cell 10 and the second perovskite cell 20. Therefore, in some optional embodiments, such as Figure 2 As shown, the solar cell structure further includes a first conductive layer 40, which is located between the back contact cell 10 and the second perovskite cell 20, so that the first conductive layer 40 can be used for conducting electricity or for reducing the recombination of carriers at the contact interface.

[0038] Optionally, the material of the first conductive layer 40 may include but is not limited to any one of indium-doped tin oxide (ITO, i.e., 90% In2O3+10% SnO2), indium-doped tungsten oxide (IWO), aluminum-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), etc., and those skilled in the art may make a reasonable selection according to actual needs. Optionally, the first conductive layer 40 may be formed by sputtering and annealing at 200°C for 10 minutes.

[0039] Exemplarily, the electron transport layer of the second perovskite cell 20 is connected in series with the first conductive layer 40, and the electron transport layer can be formed by atomic layer deposition (ALD) process with tetrakis(dimethylamino)tin(IV) (TDMASn) and H2O as precursor sources. The electron transport layer can be SnO2, and the thickness of the electron transport layer can be 20nm. During the ALD deposition, the process conditions of the atomic layer deposition (ALD) process are that the temperature of the substrate is maintained at 100°C, the tetrakis(dimethylamino)tin(IV) precursor source is 80°C, the H2O source is 18°C, the pulse and purge time of TDMASn are 1.6 seconds and 5.0 seconds, N2 is 90sccm, the H2O pulse and purge time are 1.0 seconds and 5.0 seconds, and the cycle is 140 times.

[0040] Optionally, the precursor solution of the perovskite absorption layer of the second perovskite cell 20 can be a CH3NH3PbI3 solution prepared by dissolving 1mM PbI2, methylammonium iodide (172mg) and dimethyl sulfoxide (71μL) in a dimethylformamide solvent (636.6μL). Further, the CH3NH3PbI3 solution is spin-coated on the surface of the electron transport layer away from the first conductive layer 40, and diethyl ether is dripped during the spin coating process, and then the substrate is dried on a hot plate at 60°C for 1 minute, and then dried at 100°C for 5 minutes to form the perovskite absorption layer.

[0041] Optionally, the hole transport layer of the second perovskite cell 20 is located on the surface of the perovskite absorption layer away from the electron transport layer, wherein the precursor solution of the hole transport layer can be a HTL-PTAA solution, and then the HTL-PTAA solution (7 mg / mL toluene solution) is spin coated on the perovskite absorption layer (6000 rpm, 30 s), and then annealed at 100°C for 10 minutes to form the hole transport layer.

[0042] Similarly, in order to improve the conductivity between the first perovskite absorption layer and the second perovskite absorption layer, in some optional embodiments, such as Figure 2 As shown, the solar cell structure further includes a second conductive layer 50, which is located between the first perovskite cell 30 and the second perovskite cell. Further, in order to reduce the process cost while ensuring good conductivity, the second conductive layer 50 is provided with multiple layers, wherein, illustratively, the second conductive layer 50 includes a first transparent conductive oxide layer and a first transition metal oxide layer stacked.

[0043] Specifically, the second conductive layer 50 may be a metal layer or a transparent conductive oxide layer. Exemplarily, when the second conductive layer 50 is a single layer, the material of the second conductive layer 50 may be any one of gold (Au), indium-doped tin oxide (ITO, i.e., 90% In2O3+10% SnO2), indium-doped tungsten oxide (IWO), aluminum-doped zinc oxide (AZO), and indium-doped zinc oxide (IZO). When the second conductive layer 50 includes a first transparent conductive oxide layer and a first transition metal oxide layer, exemplarily, the first transparent conductive oxide layer may be indium-doped zinc oxide (IZO), and the material of the first transition metal oxide layer may be molybdenum oxide (MoO3).

[0044] Optionally, the molybdenum oxide (MoO3) can be formed by sputtering, and the molybdenum oxide (MoO3) is located on the surface of the hole transport layer of the second perovskite cell 20 away from the perovskite absorption layer. Further, the indium-doped zinc oxide (IZO) is formed on the surface of the molybdenum oxide away from the hole transport layer of the second perovskite cell 20 by sputtering.

[0045] In some optional embodiments, the back contact cell 10 comprises a first intrinsic amorphous silicon passivation layer, a silicon substrate, a second intrinsic amorphous silicon passivation layer and a doping layer stacked in sequence, the first intrinsic amorphous silicon passivation layer is connected in series with the second perovskite cell 20, and the doping layer has the back electrode on the surface of the side away from the second intrinsic amorphous silicon passivation layer.

[0046] In the above embodiment, on the one hand, since the back contact cell 10 has a symmetrical structure with respect to the silicon substrate, the front and back sides can simultaneously receive light to generate current, thereby improving the photoelectric conversion efficiency of the solar cell, and the above back electrode forms an ohmic contact with the doping layer, which is used to extract the current collected in the solar cell structure. On the other hand, the front surface of the back contact cell 10 of the present application that contacts the second perovskite cell 20 does not originally have a metal electrode, so when the first intrinsic amorphous silicon layer of the back contact electrode is directly connected in series with the second perovskite cell 20, the structural features of the back contact cell 10 can be used to connect them in series, thereby forming the solar cell structure on the basis of a manufacturing process compatible with the back contact cell 10.

[0047] In some optional embodiments, the back contact battery 10 further includes a groove region extending from the back surface into the silicon substrate, the doping layer includes an N+ doping region and a P+ doping region, and the N+ doping region and the P+ doping region are located on both sides of the groove region.

[0048] In the above embodiment, the groove region is used to isolate the N+ doping region from the P+ doping region, thereby preventing carrier recombination in the space charge region that the doping regions may contact.

[0049] Similarly, in order to reduce the process cost of manufacturing the solar cell structure while ensuring the conductivity of the solar cell structure, in some optional embodiments, the back electrode includes a second transparent conductive oxide layer and a metal layer, and the metal layer is located on the side of the second transparent conductive oxide layer away from the second perovskite cell 20. Optionally, the material of the second transparent conductive oxide layer may include but is not limited to any one of indium-doped tin oxide (ITO, i.e. 90% In2O3+10% SnO2), indium-doped tungsten oxide (IWO), aluminum-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), etc., and the material of the metal layer may include but is not limited to metallic silver (Ag).

[0050] In some optional embodiments, the first perovskite cell 30 includes an electron transport layer, a perovskite absorption layer, a hole transport layer and an anti-reflection layer stacked in sequence, the electron transport layer is connected in series with the second perovskite cell 20, and the upper electrode is located on the exposed surface of the anti-reflection layer.

[0051] Optionally, the electron transport layer of the first perovskite absorption layer can be a SnO2 layer (20nm), which can be formed by an atomic layer deposition (ALD) process. During the ALD deposition, the process conditions corresponding to the atomic layer deposition are that the substrate temperature is maintained at 100°C, the tetrakis(dimethylamino)tin(IV) (TDMASn) precursor source is 80°C, and the H2O source is 18°C. The pulse and purge time of TDMASn is 1.6 seconds and 5.0 seconds, N2 is 90sccm, the H2O pulse and purge time are 1.0 seconds and 5.0 seconds, and the cycle is 140 times.

[0052] Optionally, a perovskite absorption layer is formed on the surface of the side of the electron transport layer away from the second conductive layer 50. The perovskite absorption layer is a wide bandgap CsPbI3 perovskite light-absorbing layer, and its preparation method can be: 350.7 mg of cesium bromide (CsI) and 622.3 mg of lead bromide (PbI2) are dissolved in 1 mL of dimethyl sulfoxide (DMSO), and then stirred and kept at 70°C overnight to obtain a CsPbI3 solution, and then the CsPbI3 perovskite solution is spin-coated on the SnO2 layer at 3000 rpm for 60 s, and annealed at 80°C for 10 min.

[0053] Optionally, a hole transport layer is formed on the side of the perovskite absorption layer of the first perovskite cell 30 away from the electron transport layer. The precursor solution of the hole transport layer can be a PTAA solution. The PTAA solution (7 mg / mL toluene solution) is spin-coated on the above-mentioned perovskite absorption layer (6000 rpm, 30s), and then annealed at 100°C for 10 minutes.

[0054] In the above embodiment, in order to further increase the photoelectric conversion efficiency, an anti-reflection layer is added to the solar cell structure, and the anti-reflection layer can reduce the surface reflectivity of the cell, thereby achieving the effect of reducing the reflection of sunlight and increasing the transmittance, so that more solar energy is absorbed by the solar cell structure. Optionally, the anti-reflection layer may include but is not limited to lithium fluoride (LiF). Optionally, the upper electrode may include but is not limited to metal gold (Au). Optionally, the lithium fluoride (LiF) may be formed by a thermal evaporation process.

[0055] In some optional embodiments, in order to extract the collection and extraction of carriers, a buffer layer is further provided between the anti-reflection layer and the hole transport layer, and the buffer layer includes a third transparent metal conductive oxide layer and a second transition metal oxide layer. Optionally, the material of the third transparent conductive oxide layer may include but is not limited to indium-doped zinc oxide (IZO), and the second transition metal oxide layer may include but is not limited to molybdenum oxide (MoO3). Optionally, the molybdenum oxide (MoO3) may be formed on the surface of the hole transport layer of the first perovskite cell 30 away from the perovskite absorption layer by a sputtering method, and further, the indium-doped zinc oxide (IZO) may be formed on the surface of the molybdenum oxide (MoO3) away from the hole transport layer of the first perovskite cell 30 by a sputtering process.

[0056] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0057] Since a solar cell structure including a back contact cell with a back electrode, a first perovskite cell with an upper electrode and a second perovskite cell is adopted, and the first perovskite cell is located on a side of the back contact cell away from the back electrode, the second perovskite cell is also located between the back contact cell and the first perovskite cell, and the upper electrode is located on a side of the first perovskite cell away from the second perovskite cell, the solar cell structure only includes two electrodes, so that relative to a stacked solar cell formed by interconnecting multiple independent sub-cells, the solar cell structure of the present application avoids the interconnection problem between two adjacent independent sub-cells; and further, the solar cell structure simultaneously has a crystalline silicon cell (back contact cell) and a perovskite cell (a first perovskite cell and a second perovskite cell). Perovskite cell), since the band gap of perovskite material is larger than the band gap of crystalline silicon material, the back contact cell as a low band gap sub-cell broadens the utilization rate of solar photons, and the first perovskite cell and the second perovskite cell as high band gap sub-cells reduce the heat energy loss in the relaxation process after the semiconductor material in the solar cell structure captures photons and the electron transition, so compared with the single junction cell, the solar cell structure of the present application has a higher ultimate photoelectric conversion efficiency, and further, the band gap of the perovskite absorption layer of the first perovskite cell in the present application is different from the band gap of the perovskite absorption layer of the second perovskite cell, so that the first perovskite cell or the second perovskite cell with a lower band gap can also be used to broaden the utilization rate of solar photons, thereby further improving the ultimate photoelectric conversion efficiency of the solar cell structure.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A solar cell structure, characterized in that: include: A back contact cell, wherein the back contact cell has a back electrode on its back surface; A first perovskite cell is located on a side of the back contact cell away from the back electrode, and a surface of the first perovskite cell on a side away from the back contact cell has an upper electrode; A second perovskite cell is located between the back contact cell and the first perovskite cell, and the band gap of the perovskite absorption layer of the first perovskite cell is different from the band gap of the perovskite absorption layer of the second perovskite cell.

2. The solar cell structure according to claim 1, characterized in that: The band gap width of the perovskite absorption layer of the first perovskite cell is greater than the band gap width of the perovskite absorption layer of the second perovskite cell.

3. The solar cell structure according to claim 1 or 2, characterized in that: The back contact cell comprises an interdigitated back contact heterojunction cell.

4. The solar cell structure according to claim 1 or 2, characterized in that: Also includes: A first conductive layer is located between the back contact cell and the second perovskite cell.

5. The solar cell structure according to claim 1 or 2, characterized in that: Also includes: The second conductive layer is located between the first perovskite cell and the second perovskite cell, and the second conductive layer includes a first transparent conductive oxide layer and a first transition metal oxide layer which are stacked.

6. The solar cell structure according to claim 1 or 2, characterized in that: The back contact cell includes a first intrinsic amorphous silicon passivation layer, a silicon substrate, a second intrinsic amorphous silicon passivation layer and a doping layer which are stacked in sequence, the first intrinsic amorphous silicon passivation layer is connected in series with the second perovskite cell, and the doping layer has the back electrode on the surface of a side away from the second intrinsic amorphous silicon passivation layer.

7. The solar cell structure according to claim 6, characterized in that: The back contact battery also includes a groove area extending from the back surface to the silicon substrate, and the doping layer includes an N+ doping area and a P+ doping area, and the N+ doping area and the P+ doping area are located on both sides of the groove area.

8. The solar cell structure according to claim 1 or 2, characterized in that: The back electrode includes a second transparent conductive oxide layer and a metal layer, wherein the metal layer is located on a side of the second transparent conductive oxide layer away from the second perovskite cell.

9. The solar cell structure according to claim 1 or 2, characterized in that: The first perovskite cell comprises an electron transport layer, a perovskite absorption layer, a hole transport layer and an anti-reflection layer stacked in sequence, the electron transport layer is connected in series with the second perovskite cell, and the upper electrode is located on an exposed surface of the anti-reflection layer.

10. The solar cell structure according to claim 9, characterized in that: A buffer layer is further provided between the anti-reflection layer and the hole transport layer. The buffer layer includes a third transparent metal conductive oxide layer and a second transition metal oxide layer.

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