A narrow-bandgap perovskite photovoltaic cell and a method of making and use thereof

Abstract

The application relates to a narrow-bandgap perovskite photovoltaic cell and a preparation method and application thereof, which sequentially comprises a substrate, a hole transport layer, a perovskite light absorption layer, an electron transport layer and an electrode layer from bottom to top; and the hole transport layer, the perovskite light absorption layer and the electron transport layer as a whole contain aspartic acid halide salt. The application is modified by aspartic acid halide salt, and an inverted structure narrow-bandgap perovskite solar cell with a photoelectric conversion efficiency of 22.26% is prepared, and on this basis, a full perovskite tandem cell with a photoelectric conversion efficiency of 26.4% is also prepared. The method can be used for preparing a solar cell device under low-temperature conditions, the overall defects of a perovskite thin film are obviously reduced, the stability of the cell is increased, and the open-circuit voltage and short-circuit current are significantly improved. In addition, good results are obtained when the method is applied to a full perovskite tandem device, and the method plays a certain guiding role for the preparation of a tin-lead narrow-bandgap perovskite solar cell and a corresponding tandem device.

Description

Technical Field

[0001] This application relates to the field of optoelectronic materials and optoelectronic devices, and in particular to a narrow bandgap perovskite photovoltaic cell, its preparation method and application. Background Technology

[0002] Due to the impact of the energy crisis, the new energy industry has developed rapidly in recent years, with perovskite solar cells showing the most rapid growth. This is mainly due to the many excellent properties of perovskite materials, such as fewer deep-level defects, excellent photoelectric properties, high quantum yield, easily tunable bandgap, long carrier lifetime, high carrier mobility, solution-processable characteristics, and low manufacturing costs; therefore, they have attracted widespread attention from researchers worldwide. As a new generation of third-generation solar cells, perovskite solar cells, after decades of development, have achieved a certified photoelectric conversion efficiency of up to 25.7% for single-junction cells. This efficiency is comparable to that of silicon solar cells, which have undergone decades of development.

[0003] Currently, common perovskite solar cell device structures mainly include two configurations: pin or nip sandwich structures. These include an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and conductive electrodes at both ends. Although single-junction perovskite cells have achieved very high photoelectric conversion efficiencies, further improvements are extremely difficult due to the Shockley-Quisser limit. Therefore, to overcome this limit, many researchers have begun to focus on all-perovskite tandem cells. This involves connecting a wide-bandgap perovskite cell with a narrow-bandgap perovskite cell in series, thereby achieving effective light absorption over a wider range and breaking through this theoretical limit. Based on this, perovskite solar cells have a wider range of application prospects.

[0004] Currently, the most commonly used all-perovskite tandem device structure by researchers worldwide is pin-type sub-cells connected in series, also known as inverted structures connected in series. However, compared to the 25.7% certified efficiency of conventional bandgap upright structures, the overall efficiency of narrow-bandgap perovskite solar cells in single-cell inverted structures is not particularly ideal. Therefore, in order to further improve the overall efficiency of all-perovskite tandem cells, how to fabricate high-efficiency narrow-bandgap perovskite solar cells is one of the main focuses of researchers.

[0005] The methods for fabricating high photoelectric conversion efficiency narrow bandgap devices that have been reported mainly include the following:

[0006] Bulk doping, the introduction of 2D phases, and post-processing of perovskite films are all methods employed. Adding cadmium iodide to the perovskite precursor solution increases the carrier diffusion length of the light-absorbing layer, further increasing the layer thickness and thus improving the battery current and overall efficiency. Alternatively, adding barium iodide to the cadmium iodide precursor creates a gradient composition in the perovskite film, further promoting carrier transport and improving device performance to 21.2%, with a short-circuit current density of 31.5 mA / cm². 2 However, all methods that increase film thickness to increase current inevitably lead to an increase in overall defects, resulting in a loss of open-circuit voltage.

[0007] By further increasing the bandgap and using phenylethyl ammonium iodide and ethylenediamine hydroiodate for post-treatment of the perovskite film to selectively anchor lead iodide and tin iodide, the generation of defects was effectively reduced, ultimately achieving a photoelectric conversion efficiency of 22.5% and an open-circuit voltage of 0.899V. However, due to the increased perovskite bandgap, it is not an ideal choice for perovskite tandem solar cells. Furthermore, considering the presence of tin in the narrow bandgap perovskite itself, its stability in outdoor water and oxygen environments is poor.

[0008] Ionic liquids with large butylammonium acetate cations were used to promote the oriented growth of tin-based perovskites in the 2D Ruddlesden-Popper phase. However, compared to traditional 3D perovskite phases, although 2D perovskites have better water and oxygen stability, they are less conducive to carrier transport.

[0009] Therefore, it is crucial for all-perovskite tandem solar cells to develop a narrow-bandgap perovskite thin film that is free of 2D phase, has good stability, and does not significantly reduce open-circuit voltage and short-circuit current density. Summary of the Invention

[0010] This application provides a narrow bandgap perovskite photovoltaic cell, its preparation method, and its application, in order to solve the problems in related technologies where narrow bandgap perovskite devices are difficult to balance stability, short-circuit current density, and open-circuit voltage.

[0011] The specific technical solution provided in this application is as follows:

[0012] In a first aspect, this application provides a narrow bandgap perovskite photovoltaic cell, which includes, from bottom to top, a substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer and an electrode layer;

[0013] Furthermore, the hole transport layer, perovskite light-absorbing layer, and electron transport layer as a whole contain aspartic acid halide.

[0014] In some embodiments, the hole transport layer is doped with aspartic acid halide;

[0015] And / or, the perovskite light-absorbing layer is doped with aspartic acid halide;

[0016] And / or, an aspartic acid halide modification layer is provided between the perovskite light-absorbing layer and the electron transport layer.

[0017] In some embodiments, the aspartic halide includes at least one of aspartic hydrochloride, aspartic hydroiodide, and aspartic hydrobromide.

[0018] In some embodiments, the electron transport layer comprises, from bottom to top, a fullerene layer and a 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline layer.

[0019] Secondly, this application also provides a method for preparing narrow bandgap perovskite photovoltaic cells as described above, comprising the following steps:

[0020] A hole transport layer precursor solution was spin-coated onto a substrate and then annealed to obtain a hole transport layer.

[0021] A perovskite precursor solution was spin-coated onto the hole transport layer and then annealed to obtain a perovskite light-absorbing layer.

[0022] An electron transport layer and an electrode layer are sequentially deposited on the perovskite light-absorbing layer.

[0023] In some embodiments, the hole transport layer precursor solution is doped with aspartic acid halide.

[0024] And / or, the perovskite precursor solution is doped with aspartic acid halide;

[0025] And / or, prior to depositing the electron transport layer, the method further includes: spin-coating an aspartic halide solution onto the perovskite light-absorbing layer, followed by heat treatment to form an aspartic halide modified layer.

[0026] In some embodiments, the hole transport layer precursor fluid comprises poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate).

[0027] In some embodiments, the perovskite precursor solution includes formamidinium hydroiodate, methylammonium iodide, lead iodide, stannous iodide, lead thiocyanate, stannous fluoride, N,N-dimethylformamide, and dimethyl sulfoxide.

[0028] In some embodiments, the preparation steps of the aspartic acid halide solution are as follows:

[0029] Aspartic acid halide was dissolved in isopropanol and mixed well to obtain an aspartic acid halide solution.

[0030] Thirdly, this application also provides the application of the narrow bandgap perovskite photovoltaic cell described above in the fabrication of all-perovskite tandem cells.

[0031] The beneficial effects of the technical solution provided in this application include:

[0032] This application modifies the hole transport layer, perovskite light-absorbing layer and electron transport layer with aspartic acid halide, which effectively improves the open-circuit voltage and short-circuit current density of the device, and can produce a pin-type narrow bandgap perovskite device with a bandgap of 1.25 eV. When applied to all-perovskite tandem cells, it can significantly improve the cell efficiency.

[0033] The narrow bandgap perovskite photovoltaic cell provided in this application can be prepared at low temperature using a solution method. The process is simple, the cost is low, and it is suitable for industrial production. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of a narrow bandgap perovskite photovoltaic cell provided in an embodiment of this application;

[0036] Figure 2 Current density-voltage curves of narrow bandgap perovskite photovoltaic cells provided in Comparative Example 1 and Examples 1-3 of this application;

[0037] Figure 3 Performance statistics of narrow bandgap perovskite photovoltaic cells provided in Comparative Example 1 and Examples 1-3 of this application are shown in the following figures. Figure 3 (a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3. Figure 3 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3. Figure 3 (c) Shows the fill factor statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3. Figure 3 (d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3;

[0038] Figure 4 This is a comparison diagram of the band structure of the perovskite solar cells provided in Example 1 and Comparative Example 1 of this application.

[0039] Figure 5 This is a comparison diagram of the external quantum efficiency of the perovskite solar cells provided in Example 1 and Comparative Example 1 of this application;

[0040] Figure 6 This is a comparison chart of the steady-state output efficiency of the perovskite solar cells provided in Example 1 and Comparative Example 1 of this application;

[0041] Figure 7 The following are performance statistics of narrow bandgap perovskite photovoltaic cells provided in Comparative Example 1 and Examples 4-6 of this application, wherein... Figure 7 (a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6. Figure 7 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6. Figure 7 (c) Shows the fill factor statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6. Figure 7 (d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6;

[0042] Figure 8 Performance statistics of narrow bandgap perovskite photovoltaic cells provided in Comparative Example 1 and Examples 7-8 of this application are shown in the following figures. Figure 8 (a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8. Figure 8 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8. Figure 8 (c) Shows the fill factor statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8. Figure 8 (d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8;

[0043] Figure 9 The following are performance statistics of narrow bandgap perovskite photovoltaic cells provided in Comparative Example 1 and Example 9 of this application, wherein... Figure 9 (a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9. Figure 9 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9. Figure 9 (c) A fill factor statistic is shown for the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9. Figure 9 (d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9;

[0044] Figure 10 This is a schematic diagram of the structure of the all-perovskite tandem solar cell provided in Embodiment 10 of this application;

[0045] Figure 11 This is a current density-voltage curve of the all-perovskite tandem solar cell provided in Example 10 of this application.

[0046] Figure reference numerals: 1. Substrate; 2. Hole transport layer; 3. Perovskite light-absorbing layer; 4. Electron transport layer; 401. Fullerene layer; 402. 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline layer; 5. Electrode layer; 6. Aspartic acid halide modification layer; 7. Wide bandgap perovskite photovoltaic cell. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings and embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0048] See Figure 1 As shown, in a first aspect, embodiments of this application provide a narrow bandgap perovskite photovoltaic cell, which includes, from bottom to top, a substrate 1, a hole transport layer 2, a perovskite light-absorbing layer 3, an electron transport layer 4, and an electrode layer 5.

[0049] Furthermore, the hole transport layer 2, the perovskite light-absorbing layer 3, and the electron transport layer 4 as a whole contain aspartic acid halide.

[0050] This application modifies the perovskite by adding aspartic acid halide salts. The amino and carboxyl groups of aspartic acid halide salts coordinate with the iodide and ammonium salts in the perovskite light-absorbing layer, and the intermolecular hydrogen bonds of aspartic acid halide salts also achieve the anchoring and passivation of the perovskite. The halide ions in the halide salts also fill and suppress the ion migration phenomenon in the perovskite, improve the properties of the film, passivate defects, and do not affect the band gap of the perovskite itself. This method significantly improves the current, voltage and stability of the device. The all-perovskite stacked device prepared based on this method has excellent overall performance.

[0051] See Figure 1 As shown, in some embodiments, the hole transport layer 2 is doped with aspartic acid halide.

[0052] And / or, the perovskite light-absorbing layer 3 is doped with aspartic acid halide;

[0053] And / or, an aspartic acid halide modification layer 6 is provided between the perovskite light-absorbing layer 3 and the electron transport layer 4.

[0054] This application provides several methods for modifying narrow-bandgap perovskite photovoltaic cells with aspartic acid halide. For ease of understanding, we will refer to "doping the hole transport layer with aspartic acid halide" as method a, "doping the perovskite light-absorbing layer with aspartic acid halide" as method b, and "setting an aspartic acid halide modification layer 6 between the perovskite light-absorbing layer and the electron transport layer" as method c. The applicant has found through research that as long as at least one of method a, method b, or method c is used for modification, the performance of the obtained device is significantly improved compared to the unmodified device.

[0055] In some embodiments, the aspartic halide includes at least one of aspartic hydrochloride, aspartic hydroiodide, and aspartic hydrobromide.

[0056] Aspartic halides with different chiralities and halogens have a significant effect on improving device performance, demonstrating the universality of aspartic halides with different chiralities.

[0057] In some embodiments, the electron transport layer 4 comprises, from bottom to top, a fullerene layer 401 and a 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline layer 402.

[0058] Furthermore, the fullerene layer 401 has a thickness of 20 nm, and the 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline layer 402 has a thickness of 7 nm.

[0059] Secondly, embodiments of this application also provide a method for fabricating narrow bandgap perovskite photovoltaic cells as described above, comprising the following steps:

[0060] A hole transport layer precursor solution was spin-coated onto substrate 1 and annealed to obtain hole transport layer 2.

[0061] A perovskite precursor solution was spin-coated onto hole transport layer 2 and annealed to obtain perovskite light-absorbing layer 3.

[0062] An electron transport layer 4 and an electrode layer 5 are sequentially deposited on the perovskite light-absorbing layer 3.

[0063] Both the hole transport layer 2 and the perovskite light-absorbing layer 3 of this application can be prepared at low temperature using a solution method. The process is simple, the cost is low, and it is suitable for industrial production.

[0064] In a preferred embodiment, the substrate further includes a pretreatment process before spin-coating the hole transport layer precursor solution:

[0065] The substrate was ultrasonically cleaned for 15 minutes each in an ultrasonic cleaner using deionized water, acetone, isopropanol, and ethanol containing glass cleaning agent. After ultrasonic cleaning, the substrate was dried with nitrogen gas to obtain a clean substrate.

[0066] Specifically, the substrate is an indium-doped tin oxide substrate.

[0067] Specifically, the step of "spin-coating a hole transport layer precursor solution onto substrate 1, annealing, and obtaining hole transport layer 2" includes:

[0068] Hole transport layer precursor solution was spin-coated onto substrate 1 at a spin speed of 5000 r.mp for 30 s. After spin-coating, the substrate was annealed at 140 °C for 30 min to obtain hole transport layer 2.

[0069] Specifically, "spin-coating perovskite precursor solution onto hole transport layer 2, followed by annealing to obtain perovskite light-absorbing layer 3" includes:

[0070] Perovskite precursor solution was spin-coated onto hole transport layer 2 at a spin speed of 4000 rpm for 40 seconds. After 20 seconds of spin-coating, 400 μL of chlorobenzene solvent was added dropwise. After spin-coating was completed, the mixture was annealed at 100 °C for 10 minutes.

[0071] Specifically, the method for preparing the electron transport layer 4 is as follows:

[0072] Fullerene layer 401 is formed by vacuum thermal evaporation of fullerene.

[0073] 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline is vacuum thermally deposited on the surface of fullerene layer 401 to form 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline layer 402.

[0074] The method for preparing the electrode layer 5 is as follows:

[0075] Cu is vacuum thermally deposited on the surface of the 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline layer 402 to form the electrode layer 5.

[0076] Furthermore, the electrode layer 5 has a thickness of 80 nm.

[0077] In some embodiments, the hole transport layer precursor solution is doped with aspartic acid halide.

[0078] And / or, the perovskite precursor solution is doped with aspartic acid halide;

[0079] And / or, before evaporating the electron transport layer 4, the method further includes: spin-coating an aspartic acid halide solution onto the perovskite light-absorbing layer 3, followed by heat treatment to form an aspartic acid halide modification layer 6.

[0080] Specifically, "spin-coating an aspartic acid halide solution onto the perovskite light-absorbing layer 3, followed by heat treatment to form an aspartic acid halide modified layer 6" specifically includes:

[0081] An aspartic acid halide solution was spin-coated onto the perovskite light-absorbing layer 3 at a spin speed of 5000 r.mp for 30 s. After spin-coating, the layer was heated at 90°C for 7 min to obtain the aspartic acid halide modified layer 6.

[0082] In some embodiments, the hole transport layer precursor fluid comprises poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate).

[0083] Furthermore, the preparation method of the hole transport layer precursor solution doped with aspartic halide includes the following steps:

[0084] Take a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) stock solution, weigh a certain amount of aspartic acid halide salt into the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) stock solution, the concentration of which is 1-10 mg / ml, and place it on a shaker at 25℃ and mix for 2 hours.

[0085] In some embodiments, the perovskite precursor solution includes formamidinium hydroiodate, methylammonium iodide, lead iodide, stannous iodide, lead thiocyanate, stannous fluoride, N,N-dimethylformamide, and dimethyl sulfoxide.

[0086] Furthermore, the preparation method of perovskite precursor solution doped with aspartic halide includes the following steps:

[0087] (1) Prepare formamidin hydroiodate: methyl ammonium iodide = 7:3 respectively;

[0088] Lead iodide: stannous iodide = 5:5;

[0089] Lead thiocyanate : (formamidinium hydroiodate + methylammonium iodide) = 0.0075 : 1;

[0090] Stannous fluoride : Stannous iodide = 0.1 : 1;

[0091] Weigh out a certain amount of the drug in a molar ratio of aspartic acid halide (formamidinium hydroiodate + methylammonium iodide) = 0.0025 to 0.02:1;

[0092] (2) Dissolve all the reagents prepared in step (1) in a mixed solvent of N,N-dimethylformamide:dimethyl sulfoxide = 3:1 (volume ratio) to obtain a 1.8M orange-yellow solution. Place the solution on a shaker at 25°C and mix for 3 hours to obtain a perovskite precursor solution.

[0093] Excess stannous fluoride is used to stabilize the perovskite, and a small amount of lead thiocyanate is added to improve the film quality. Finally, it contacts the electron transport layer 4 and the hole transport layer 2 to form a pin-type inverted battery device.

[0094] Aspartic acid halides utilize their amino and carboxyl groups to coordinate with lead iodide and stannous iodide, as well as their own intermolecular hydrogen bonds, to anchor and passivate perovskites.

[0095] In some embodiments, the preparation steps of the aspartic acid halide solution are as follows:

[0096] Aspartic acid halide was dissolved in isopropanol and mixed well to obtain an aspartic acid halide solution.

[0097] Furthermore, the concentration of the aspartic acid halide solution is 0.1–1 mg / ml.

[0098] Specifically, after dissolving the aspartic acid halide in isopropanol, the solution is placed on a shaker at 60°C and mixed for 2 hours to obtain an aspartic acid halide solution.

[0099] Thirdly, embodiments of this application also provide the application of the narrow bandgap perovskite photovoltaic cell described above in the fabrication of an all-perovskite tandem cell.

[0100] The narrow bandgap perovskite photovoltaic cell provided in this application has high open-circuit voltage and short-circuit current density. The fabricated tin-lead narrow bandgap perovskite device has a pin-type structure and a bandgap of 1.25 eV, which is an ideal candidate bandgap for narrow bandgap in all-perovskite tandem cells, and can further improve the efficiency of all-perovskite tandem cells.

[0101] The present application will be further described below through specific embodiments.

[0102] Example 1

[0103] A method for fabricating a narrow bandgap perovskite photovoltaic cell includes the following steps:

[0104] 101. Cleaning of indium-doped tin oxide substrates:

[0105] The etched indium-doped tin oxide (2×2cm) was ultrasonically cleaned for 15 minutes each in an ultrasonic cleaner with deionized water, acetone, isopropanol and ethanol containing glass cleaning agent. After ultrasonic cleaning, it was dried with nitrogen gas to obtain a clean substrate.

[0106] 102. Preparation of the hole transport layer:

[0107] Take a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) stock solution, weigh a certain amount of DL-aspartic acid hydrochloride and dissolve it in the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) stock solution, the concentration of which is 4 mg / ml, and place the resulting solution on a shaker at 25℃ and mix for 2 h;

[0108] In an environment with an air humidity of 40%, the spin coater was set to a speed of 5000 rpm. A poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) solution was dropped onto an indium-doped tin oxide substrate, spin-coated for 30 seconds, and then annealed at 140°C for 30 minutes.

[0109] 103. Preparation of the perovskite light-absorbing layer:

[0110] (1) Prepare formamidin hydroiodate: methyl ammonium iodide = 7:3 respectively;

[0111] Lead iodide: stannous iodide = 5:5;

[0112] Lead thiocyanate : (formamidinium hydroiodate + methylammonium iodide) = 0.0075 : 1;

[0113] Stannous fluoride : Stannous iodide = 0.1 : 1;

[0114] Weigh a certain amount of the drug at a molar ratio of DL-aspartic acid hydrochloride: (formamidin hydroiodide + methylammonium iodide) = 0.01:1;

[0115] (2) Dissolve all the reagents prepared in step (1) in a mixed solvent of N,N-dimethylformamide:dimethyl sulfoxide = 3:1 (volume ratio) to obtain a 1.8M orange-yellow solution, place it on a shaker at 25°C and mix for 3 hours to obtain a perovskite precursor solution;

[0116] (3) Transfer the substrate with the hole transport layer spin-coated to a glove box where the water and oxygen values ​​are both below 0.1 ppm. Spin-coat the perovskite precursor solution onto the hole transport layer at a speed of 4000 r.pm for 40 s. Add 400 μL of chlorobenzene solvent 20 s before the end of the spin-coating. Then anneal on a hot plate at 100 ℃ for 10 min.

[0117] 104. Preparation of aspartic acid halide modified layer:

[0118] A certain amount of DL-aspartic acid hydrochloride was weighed and placed in isopropanol solution with a concentration of 0.2 mg / ml. The resulting solution was placed on a shaker at 60℃ and mixed for 2 hours to obtain an aspartic acid halide solution.

[0119] The spin coater was set to a speed of 5000 rpm and a spin coating time of 30 s. Aspartic acid halide solution was spin-coated onto the perovskite light-absorbing layer, and then heated on a hot stage at 90 ℃ for 7 min.

[0120] 105. Fabrication of the electron transport layer:

[0121] The prepared thin film was inverted onto the sample substrate and then transferred to a high-vacuum evaporation apparatus, where the chamber was evacuated to a vacuum level of 2.0 × 10⁻⁶. -4 Pa, sequentially deposited 20 nm of fullerene and 7 nm of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline;

[0122] 106. Preparation of the electrode layer:

[0123] The evaporated film was inverted onto another sample substrate and then transferred to another high-vacuum evaporation apparatus, where the chamber was evacuated to a vacuum of 4.0 × 10⁻⁶. -4 Pa, and then an 80 nm thick Cu electrode is deposited by vapor deposition.

[0124] Example 2

[0125] It includes most of the operational steps of Example 1, with the only difference being:

[0126] The perovskite light-absorbing layer is not doped with DL-aspartic acid hydrochloride, and no aspartic acid halide modification layer is prepared.

[0127] Example 3

[0128] It includes most of the operational steps of Example 1, with the only difference being:

[0129] The perovskite light-absorbing layer is not doped with DL-aspartic acid hydrochloride.

[0130] Example 4

[0131] 101. Cleaning of indium-doped tin oxide substrate: Same as in Example 1.

[0132] 102. Preparation of the hole transport layer:

[0133] It is not doped with DL-aspartic acid hydrochloride, otherwise it is the same as in Example 1.

[0134] 103. Preparation of the perovskite light-absorbing layer: Same as in Example 1.

[0135] 104. Preparation of aspartic acid halide modified layer:

[0136] This step is not performed.

[0137] 105. Preparation of the electron transport layer: Same as in Example 1.

[0138] 106. Preparation of electrode layer: Same as in Example 1.

[0139] Example 5

[0140] It includes most of the operational steps of Example 4, the only difference being:

[0141] The aspartic halide doped in the perovskite light-absorbing layer is D-aspartic hydrochloride.

[0142] Example 6

[0143] It includes most of the operational steps of Example 4, the only difference being:

[0144] The aspartic halide doped in the perovskite light-absorbing layer is L-aspartic hydrochloride.

[0145] Example 7

[0146] It includes most of the operational steps of Example 1, with the only difference being:

[0147] The aspartic halide doped in the perovskite light-absorbing layer is DL-aspartic hydroiodide.

[0148] Example 8

[0149] It includes most of the operational steps of Example 1, with the only difference being:

[0150] The aspartic halide doped in the perovskite light-absorbing layer is DL-aspartic hydrobromide.

[0151] Example 9

[0152] 101. Cleaning of indium-doped tin oxide substrate: Same as in Example 1.

[0153] 102. Preparation of the hole transport layer:

[0154] It is not doped with DL-aspartic acid hydrochloride, otherwise it is the same as in Example 1.

[0155] 103. Preparation of the perovskite light-absorbing layer:

[0156] It is not doped with DL-aspartic acid hydrochloride, otherwise it is the same as in Example 1.

[0157] 104. Preparation of aspartic acid halide modified layer:

[0158] The aspartic acid halide is DL-aspartic acid hydrobromide, and the rest is the same as in Example 1.

[0159] 105. Preparation of the electron transport layer: Same as in Example 1.

[0160] 106. Preparation of electrode layer: Same as in Example 1.

[0161] Example 10

[0162] A method for fabricating an all-perovskite tandem solar cell includes the following steps:

[0163] 101. Take a wide-bandgap solar cell 7, which, from bottom to top, includes an indium-doped tin oxide substrate, a [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid layer, a wide-bandgap perovskite light-absorbing layer, a fullerene layer, and a tin oxide / gold layer.

[0164] 102: Hole transport layer 2, perovskite light-absorbing layer 3, aspartic acid halide modified layer 6, electron transport layer 4, and electrode layer 6 were sequentially prepared on the tin oxide / gold layer according to the steps of Example 1 to obtain an all-perovskite tandem solar cell. See [link to example]. Figure 10 .

[0165] Comparative Example 1

[0166] It includes most of the operations of Example 1, except that:

[0167] The hole transport layer is not doped with DL-aspartic acid hydrochloride, the perovskite light-absorbing layer is not doped with DL-aspartic acid hydrochloride, and no aspartic acid halide modification layer is prepared.

[0168] Performance testing

[0169] The devices prepared in Examples 1-10 and Comparative Example 1 were subjected to a series of photoelectric tests using the IVS-KA6000 solar simulator testing system. After adding a mask, the effective area of ​​the device was 0.070225 cm². 2 The test was conducted under the specified conditions.

[0170] See Figure 2 As shown, Figure 2 The current density-voltage curves of narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3 are shown. As can be seen from the figures, the DL mixed chiral aspartic acid hydrochloride doped in Examples 1-3 performs better than Comparative Example 1 under various conditions, indicating that the modification of aspartic acid halide can effectively improve the performance of narrow bandgap perovskite photovoltaic cells, with the best device efficiency reaching 22.26%.

[0171] See Figure 3 As shown, where, Figure 3 (a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3. Figure 3 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3. Figure 3 (c) Shows the fill factor statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3. Figure 3(d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 1-3. As can be seen from the figure, the performance improvement of the devices modified with aspartic acid halide in Examples 1-3 is mainly concentrated in the open circuit voltage and short circuit current density.

[0172] See Figure 4 As shown, Figure 4 The diagram shows a comparison of the energy bands of the perovskite solar cells prepared in Example 1 and Comparative Example 1. As can be seen from the diagram, the conduction band position of the perovskite in the device prepared in Example 1 is lower, which is more compatible with the conduction band energy level of the electron transport layer. At the same time, the low valence band is also more compatible with the valence band energy level of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), resulting in a higher open-circuit voltage.

[0173] See Figure 5 As shown, Figure 5 The accompanying graph shows a comparison of the external quantum efficiency of the narrow bandgap perovskite solar cells prepared in Example 1 and Comparative Example 1. As can be seen from the figure, the external quantum efficiency of the device prepared in Example 1 is significantly higher in the long wavelength range. This may be attributed to the passivation of defects and the improved ability to extract carriers from the perovskite layer.

[0174] See Figure 6 As shown, Figure 6 The diagram shows a comparison of the steady-state output efficiency of the narrow bandgap perovskite solar cells prepared in Example 1 and Comparative Example 1. The device prepared in Example 1 has a better steady-state output efficiency than that in Comparative Example 1, which is attributed to the device's all-around passivation effect and the suppression of perovskite halide ion migration.

[0175] See Figure 7 As shown, where, Figure 7 (a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6. Figure 7 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6. Figure 7 (c) Shows the fill factor statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6. Figure 7 (d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 4-6. As can be seen from the figure, the devices modified with different chiral aspartic halide salts in Examples 4-6 all showed different degrees of performance improvement compared with the unmodified devices, indicating the universality of different chiral aspartic halide salts.

[0176] See Figure 8 As shown, where, Figure 8(a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8. Figure 8 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8. Figure 8 (c) Shows the fill factor statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8. Figure 8 (d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Examples 7-8. As can be seen from the figure, the devices prepared by modifying the perovskite light-absorbing layer with different halogens of aspartic acid halide salts in Examples 7-8 all showed different degrees of performance improvement compared with the unmodified devices, indicating the universality of different halogens of aspartic acid halide salts.

[0177] See Figure 9 As shown, where, Figure 9 (a) shows the short-circuit current density statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9. Figure 9 (b) Shows the open-circuit voltage statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9. Figure 9 (c) A fill factor statistic is shown for the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9. Figure 9 (d) shows the photoelectric conversion efficiency statistics of the narrow bandgap perovskite photovoltaic cells prepared in Comparative Example 1 and Example 9. The device obtained by preparing the aspartic halide modification layer with chiral aspartic hydrobromide in Example 9 showed different degrees of performance improvement compared with the unmodified device, further demonstrating the universality of aspartic halide salts with different halogens.

[0178] See Figure 11 As shown, Figure 11 The current density-voltage curve of the all-perovskite tandem solar cell prepared in Example 10 is shown. As can be seen from the figure, the high-efficiency narrow bandgap perovskite solar cell provided in this application was applied to the all-perovskite tandem solar cell and finally achieved a high efficiency of 26.4%, which further expands the applicability of this method.

[0179] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0180] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A narrow bandgap perovskite photovoltaic cell, characterized in that, From bottom to top, it includes a substrate (1), a hole transport layer (2), a perovskite light-absorbing layer (3), an electron transport layer (4), and an electrode layer (5). Furthermore, the hole transport layer (2), the perovskite light-absorbing layer (3), and the electron transport layer (4) as a whole contain aspartic acid halide. The hole transport layer (2) is doped with aspartic acid halide; And / or, the perovskite light-absorbing layer (3) is doped with aspartic acid halide; And / or, an aspartic acid halide modification layer (6) is provided between the perovskite light-absorbing layer (3) and the electron transport layer (4).

2. The narrow bandgap perovskite photovoltaic cell as described in claim 1, characterized in that, The aspartic halide includes at least one of aspartic hydrochloride, aspartic hydroiodide, and aspartic hydrobromide.

3. The narrow bandgap perovskite photovoltaic cell as described in claim 1, characterized in that, The electron transport layer (4) comprises, from bottom to top, a fullerene layer (401) and a 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline layer (402).

4. The method for preparing narrow bandgap perovskite photovoltaic cells as described in claim 1, characterized in that, Includes the following steps: Hole transport layer precursor liquid was spin-coated onto substrate (1) and annealed to obtain hole transport layer (2). A perovskite precursor solution was spin-coated onto the hole transport layer (2) and annealed to obtain a perovskite light-absorbing layer (3). An electron transport layer (4) and an electrode layer (5) are sequentially deposited on the perovskite light-absorbing layer (3).

5. The method for preparing a narrow bandgap perovskite photovoltaic cell as described in claim 4, characterized in that, The hole transport layer precursor solution is doped with aspartic acid halide. And / or, the perovskite precursor solution is doped with aspartic acid halide; And / or, before evaporating the electron transport layer (4), the method further includes: spin-coating an aspartic acid halide solution onto the perovskite light-absorbing layer (3), followed by heat treatment to form an aspartic acid halide modified layer (6).

6. The method for preparing a narrow bandgap perovskite photovoltaic cell as described in claim 4, characterized in that, The hole transport layer precursor fluid comprises poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate).

7. The method for preparing a narrow bandgap perovskite photovoltaic cell as described in claim 4, characterized in that, The perovskite precursor solution includes formamidinium hydroiodate, methylammonium iodide, lead iodide, stannous iodide, lead thiocyanate, stannous fluoride, N,N-dimethylformamide, and dimethyl sulfoxide.

8. The method for preparing a narrow bandgap perovskite photovoltaic cell as described in claim 5, characterized in that, The preparation steps of the aspartic acid halide solution are as follows: Aspartic acid halide was dissolved in isopropanol and mixed well to obtain an aspartic acid halide solution.

9. The application of the narrow bandgap perovskite photovoltaic cell as described in any one of claims 1-3 in the preparation of an all-perovskite tandem cell.

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