Perovskite solar cell and preparation method thereof

Abstract

The application provides a perovskite solar cell and a preparation method thereof. The perovskite solar cell comprises a transparent conductive layer, an electron transport layer, a perovskite light-absorbing layer and a hole transport layer which are sequentially stacked, and the electron transport layer comprises titanium dioxide and a trivalent iron compound. The application can improve the photoelectric performance and efficiency of the perovskite solar cell.

Description

Technical Field

[0001] This invention relates to the field of solar cells, specifically to a perovskite solar cell and its fabrication method. Background Technology

[0002] In recent years, perovskite solar cells have attracted widespread attention due to their advantages such as long carrier diffusion length, tunable bandgap, high light absorption coefficient, and low raw material cost. For example, halide perovskite solar cells are considered third-generation solar cells, and the efficiency of single-junction lead-based perovskite solar cells can rival that of silicon-based solar cells. However, the photoelectric performance and efficiency of existing perovskite solar cells still need to be improved. Summary of the Invention

[0003] This invention provides a perovskite solar cell and its preparation method, which can improve the photoelectric performance and efficiency of perovskite solar cells.

[0004] In one aspect, the present invention provides a perovskite solar cell comprising a transparent conductive layer, an electron transport layer, a perovskite light-absorbing layer and a hole transport layer stacked sequentially, wherein the electron transport layer comprises titanium dioxide and a trivalent iron compound.

[0005] According to one embodiment of the present invention, the electron transport layer includes a dense electron transport layer and a mesoporous electron transport layer located between the dense electron transport layer and the perovskite light-absorbing layer, wherein the trivalent iron compound is present in the dense electron transport layer.

[0006] According to one embodiment of the present invention, in the dense electron transport layer, the molar ratio of iron to titanium is 1:(300-650).

[0007] According to one embodiment of the present invention, the transparent conductive layer comprises FTO conductive glass.

[0008] In another aspect, the present invention provides a method for preparing the above-mentioned perovskite solar cell, comprising the following steps: coating a first mixture containing an organic titanium source, an iron source for forming the trivalent iron compound, and a first solvent onto a transparent conductive layer to form a dense electron transport layer; coating a second mixture containing an inorganic titanium source and a second solvent onto the dense electron transport layer to form a mesoporous electron transport layer; and sequentially forming a perovskite light-absorbing layer and a hole transport layer on the mesoporous electron transport layer to obtain the perovskite solar cell.

[0009] According to one embodiment of the present invention, before the first mixture is applied to the transparent conductive layer, the transparent conductive layer is pretreated. The pretreatment process includes: cleaning the transparent conductive layer with a cleaning agent, drying it, and then performing ultraviolet ozone treatment; wherein the cleaning agent includes one or more of water, acetone, isopropanol, ethanol, and glass cleaner.

[0010] According to one embodiment of the present invention, the organic titanium source comprises titanium diisopropoxybisacetylacetonate; and / or, the iron source comprises iron acetylacetonate; and / or, the molar ratio of iron in the iron source to titanium in the organic titanium source is 1:(300-650); and / or, the first solvent comprises n-butanol.

[0011] According to one embodiment of the present invention, the organic titanium source includes titanium diisopropoxybisacetylacetonate, the iron source includes iron acetylacetonate, and the process of forming the first mixture includes: mixing the titanium diisopropoxybisacetylacetonate with the iron acetylacetonate, and then adding a first solvent to the obtained mixture to obtain the first mixture; wherein, the volume ratio of the mixture to the first solvent is 1:14 to 18.

[0012] According to one embodiment of the present invention, the first mixture is spin-coated onto the transparent conductive layer using a dynamic spin-coating method, and then annealed at 110-130°C for 8-12 minutes to form the dense electron transport layer.

[0013] According to one embodiment of the present invention, the inorganic titanium source includes titanium dioxide; and / or, the second solvent includes ethanol; and / or, the second mixture is spin-coated onto the dense electron transport layer using a static spin-coating method, and then annealed at 450-550°C for 40-70 min to form the mesoporous electron transport layer.

[0014] In this invention, a ferric compound is introduced into the electron transport layer of a perovskite solar cell, thereby doping the electron transport layer with ferric ions (Fe). 3+ This invention optimizes the performance of the electron transport layer, thereby improving the photoelectric performance and efficiency of perovskite solar cells. Furthermore, the perovskite solar cells of this invention have advantages such as simple fabrication process and ease of operation, facilitating practical industrial applications. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell according to an embodiment of the present invention;

[0016] Figure 2The steady-state photoluminescence spectra of the perovskite solar cells of Example 1 and Comparative Example 1 are shown (the horizontal axis represents wavelength, and the vertical axis represents photoluminescence intensity).

[0017] Figure 3 The transient photoluminescence spectra of the perovskite solar cells of Example 1 and Comparative Example 1 are shown (the horizontal axis is time, and the vertical axis is normalized photoluminescence intensity).

[0018] Figure 4 This is a photograph of the perovskite solar cell prepared in Example 1.

[0019] Explanation of reference numerals in the attached figures: 1: Transparent conductive layer; 11: First region; 12: Second region; 2: Electron transport layer; 21: Dense electron transport layer; 22: Mesoporous electron transport layer; 3: Perovskite light-absorbing layer; 4: Hole transport layer; 5: Counter electrode. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In recent years, perovskite solar cells have attracted widespread attention due to their advantages such as long carrier diffusion length, tunable bandgap, high light absorption coefficient, and low raw material cost. However, the photoelectric performance and efficiency of existing perovskite solar cells still need to be improved.

[0022] For example, the main functional layers of a perovskite solar cell include an electron transport layer, a perovskite light-absorbing layer, and a hole transport layer, also known as a "sandwich" structure. The electron transport layer lowers the potential barrier between the electrode and the perovskite, promoting carrier migration, and effectively blocks holes, thus suppressing electron-hole recombination at the interface. It is crucial for high-efficiency and stable perovskite solar cells. In both formal and inverse structures, electron transport layer materials typically include titanium dioxide (TiO2), tin dioxide (SnO2), and PCBM. TiO2 is a commonly used electron transport layer material in mesoporous nip-type perovskite solar cells. However, pure TiO2 suffers from a large bandgap, low electron mobility, and easy degradation under ultraviolet light. Furthermore, the fabrication of dense electron transport layers using methods such as dynamic spin-coating also presents defects, such as oxygen vacancy defects. The presence of oxygen vacancy defects can lead to the formation of two surrounding TiO2 layers. 4+ Become Ti 3+ This traps photogenerated electrons generated by the perovskite light-absorbing layer, adversely affecting the photoelectric conversion efficiency and stability of the battery device.

[0023] Therefore, embodiments of the present invention provide a perovskite solar cell, such as... Figure 1 As shown, the perovskite solar cell includes a transparent conductive layer 1, an electron transport layer 2, a perovskite light-absorbing layer (perovskite thin film layer) and a hole transport layer 4 stacked sequentially. The electron transport layer 2 includes TiO2 and a trivalent iron compound.

[0024] In this embodiment of the invention, based on the properties of the electron transport layer 2 in the perovskite solar cell, Fe is doped into the electron transport layer 2 by introducing a trivalent iron compound into the electron transport layer 2. 3+ Optimize the performance of electron transport layer 2 to improve the photoelectric performance and efficiency of perovskite solar cells. For example, it can effectively improve the open-circuit voltage and photoelectric conversion efficiency of perovskite solar cells.

[0025] According to the inventor's research and analysis, based on Fe 3+ With Ti 4+ Similar ionic radii and other properties, Fe 3+ Fe can diffuse into the TiO2 lattice; therefore, by doping Fe into the TiO2-containing electron transport layer 2... 3+ This can effectively promote the extraction and transport of photogenerated electrons, thereby improving the photoelectric conversion efficiency and other performance characteristics of perovskite solar cells. Therefore, by introducing a trivalent iron compound into the electron transport layer 2, charge transport between the electron transport layer 2 and the perovskite light-absorbing layer 3 can be promoted, enhancing the fluorescence quenching effect and improving the photoelectric performance and efficiency of the perovskite solar cell.

[0026] Further research revealed that the aforementioned trivalent iron compounds may include iron acetylacetonate, which is more conducive to synergistic effects with TiO2, optimizing the performance of electron transport layer 2 and further improving the photoelectric performance and efficiency of perovskite solar cells.

[0027] Generally, the electron transport layer 2 can be a titanium dioxide layer, that is, TiO2 forms the matrix of the electron transport layer 2, and trivalent iron compounds are dispersed in the matrix.

[0028] Continue to refer to Figure 1 The electron transport layer 2 may include a dense electron transport layer 21 (dense thin film layer) and a mesoporous electron transport layer 22 (mesoporous thin film layer) located between the dense electron transport layer 21 and the perovskite light-absorbing layer 3.

[0029] Specifically, the dense electron transport layer 21 and the mesoporous electron transport layer 22 may each include TiO2. Furthermore, both the dense electron transport layer 21 and the mesoporous electron transport layer 22 may be titanium dioxide layers, that is, the dense electron transport layer 21 is a dense titanium dioxide layer (c-TiO2), and the mesoporous electron transport layer 22 is a mesoporous titanium dioxide layer (m-TiO2).

[0030] In some embodiments, a ferric compound is present in the dense electron transport layer 21, that is, the dense electron transport layer 21 in the embodiments of the present invention is a dense electron transport layer 21 doped with ferric ions. This is beneficial to further optimize the performance of the electron transport layer 2 and improve the photoelectric performance and efficiency of the perovskite solar cell.

[0031] Specifically, according to the research of the present invention, on the one hand, the introduction of trivalent iron compounds into the dense electron transport layer 21 is beneficial to its charge transport function; on the other hand, defects such as oxygen vacancy defects exist during the preparation of the dense electron transport layer 21 by methods such as dynamic spin coating. The presence of oxygen vacancy defects can lead to the formation of two Ti atoms around the layer. 4+ Become Ti 3+ This traps photogenerated electrons generated by the perovskite light-absorbing layer 3, negatively impacting the photoelectric conversion efficiency and stability of the battery device. However, by introducing a trivalent iron compound into the dense electron transport layer 21, the dense electron transport layer 21 is doped with Fe. 3+ This can effectively overcome these problems, thereby optimizing the performance of the dense electron transport layer 21 and improving the photoelectric performance and efficiency of perovskite solar cells.

[0032] Specifically, in the aforementioned dense electron transport layer 21, the molar ratio of iron to titanium is 1:(300-650) (that is, in terms of iron and titanium, the molar ratio of trivalent iron compound to titanium dioxide is 1:(300-650)), for example, 1:300, 1:330, 1:350, 1:380, 1:400, 1:430, 1:450, 1:480, 1:500, 1:530, 1:550, 1:580, 1:600, 1:630, 1:650 or any combination thereof.

[0033] In this invention, the mesoporous electron transport layer 22 may have the mesoporous morphology and structure of a conventional mesoporous electron transport layer 22 in the art, and the dense electron transport layer 21 may have the dense morphology and structure of a conventional dense electron transport layer 21 in the art, without any particular limitation.

[0034] Furthermore, the aforementioned transparent conductive layer 1 is formed of a transparent conductive material, which may specifically include transparent conductive glass. In some preferred embodiments, the aforementioned transparent conductive layer 1 may include FTO (fluorine-doped tin oxide) conductive glass.

[0035] In addition, the perovskite absorber layer described above may include metal halides and / or organohalides. Metal halides may include metal iodides, such as lead iodide; organohalides may include organoiodides and / or organochlorides, such as formamidine and / or chloromethylamine, but are not limited thereto.

[0036] Furthermore, the aforementioned hole transport layer 4 includes a hole transport material, such as a Spiro-OMeTAD hole transport layer 4 formed by Spiro-OMeTAD.

[0037] Under normal circumstances, such as Figure 1 As shown, the perovskite solar cell also includes a counter electrode 5, which may include a metal, such as a metal electrode formed of a metal, such as gold (Au).

[0038] Continue to refer to Figure 1 The transparent conductive layer 1, facing the perovskite light-absorbing layer 3, includes a first region 11 and a second region 12 (or conductive region). An electron transport layer 2, a perovskite light-absorbing layer 3, and a hole transport layer 4 are sequentially stacked on the first region 11 of the transparent conductive layer 1, meaning the first region 11 is covered by these layers, while the second region 12 is not. Counter electrodes 5 are respectively provided on the side of the hole transport layer 4 facing away from the perovskite light-absorbing layer 3 and on the second region 12. Specifically, as shown... Figure 1 what Figure 4 As shown, the counter electrode 5 has multiple (such as) Figure 1 As shown, the number of counter electrodes 5 is 7; or as... Figure 4 As shown, there are 9 counter electrodes 5, one of which is disposed in the second region 12 of the transparent conductive layer 1, and the remaining counter electrodes 5 are disposed on the side of the hole transport layer 4 away from the perovskite light-absorbing layer 3. These counter electrodes 5 can be uniformly distributed on the side of the hole transport layer 4 away from the perovskite light-absorbing layer 3, for example, they can be arrayed on the side of the hole transport layer 4 away from the perovskite light-absorbing layer 3.

[0039] This invention also provides a method for preparing the above-mentioned perovskite solar cell, the method comprising the following steps:

[0040] S1. Pre-treatment of the transparent conductive layer 1 includes: cleaning the transparent conductive layer 1 with a cleaning agent, drying it, and then performing ultraviolet ozone treatment; wherein the cleaning agent includes one or more of water, acetone, isopropanol, ethanol, and glass cleaner.

[0041] The glass cleaner can be a conventional glass cleaner in the art, such as one that includes surfactants and water, and can be commercially available or made in-house according to conventional methods in the art, without particular limitation.

[0042] In practice, multiple cleaning agents can be used to ultrasonically clean the transparent conductive layer 1 (such as FTO conductive glass) in sequence. For example, water, glass cleaner, isopropanol, ethanol and water can be used sequentially to ultrasonically clean the transparent conductive layer 1 (the mass ratio of glass cleaner to water is approximately 1:3). Alternatively, acetone, isopropanol, ethanol and water can be used sequentially to ultrasonically clean the transparent conductive layer 1. Each cleaning time can be 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes or any combination thereof. Then, it can be placed in a drying equipment such as an oven for drying. The drying temperature can be 110 to 130°C, for example, 110°C, 115°C, 120°C, 125°C, 130°C or any combination thereof, to remove impurities and moisture from the surface of the transparent conductive layer 1. Then, ultraviolet ozone treatment is performed.

[0043] The water used can specifically include deionized water.

[0044] The ultraviolet ozone treatment time can be 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes or any combination thereof.

[0045] In the above process, ultraviolet ozone treatment can oxidize and degrade organic matter on the surface of transparent conductive layer 1, and can enhance the work function of the surface of transparent conductive layer 1, which is beneficial to electron transport.

[0046] The embodiments of the present invention may use conventional devices in the art, such as ultraviolet-ozone generators, for ultraviolet ozone treatment, and there are no particular limitations thereto.

[0047] S2. A first mixture containing an organic titanium source, an iron source for forming the above-mentioned trivalent iron compound, and a first solvent is coated onto the transparent conductive layer 1 to form a dense electron transport layer 21.

[0048] Specifically, the first mixture can be spin-coated onto the transparent conductive layer 1 using a dynamic spin-coating method. Specifically, the first mixture can be spin-coated onto the transparent conductive layer 1 at a rotation speed of 1500 to 2500 rpm (the rotation speed can be any combination of 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, 2100 rpm, 2200 rpm, 23000 rpm, 2400 rpm, 2500 rpm, or any two of these speeds). After a first drying process, a dense electron transport layer 21 is formed.

[0049] Specifically, the first drying process may include an annealing process, the temperature of which may be 110 to 130°C, for example, a range of 110°C, 115°C, 120°C, 125°C, 130°C or any two of these, and the time may be 8 to 12 minutes, for example, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes or any two of these.

[0050] In some embodiments, the first mixture is spin-coated onto the transparent conductive layer 1 using a dynamic spin-coating method, and then annealed at 110–130°C for 8–12 min to form a dense electron transport layer 21.

[0051] In the above process, after the first drying treatment, the organic titanium source is converted into TiO2, that is, the dense electron transport layer 21 is a dense titanium dioxide layer, and the iron source forms a trivalent iron compound dispersed in the dense electron transport layer 21, thereby making the dense electron transport layer 21 doped with trivalent iron ions.

[0052] Specifically, the organic titanium source may include diisopropoxydiacetylacetonate.

[0053] In addition, the iron source mentioned above may include an organic iron source, wherein the iron element may be trivalent, and iron acetylacetone is generally preferred.

[0054] Furthermore, the amount of iron source is controlled such that the molar ratio of iron in the iron source to titanium in the organic titanium source is 1:(300-650). By adding a low concentration of iron source, an appropriate amount of ferric ions is introduced into the dense electron transport layer 21 (the molar ratio of iron to titanium in the dense electron transport layer 21 is 1:(300-650)), which can further optimize the performance of the dense electron transport layer 21, thereby further improving the photoelectric performance and efficiency of the perovskite solar cell.

[0055] In practice, the organic titanium source and the iron source can be mixed, and then the first solvent can be added to the resulting mixture. The mixture can be stirred evenly, for example, for 50 to 70 minutes, to obtain the first mixture.

[0056] In some preferred embodiments, the process of forming the first mixture includes: mixing diisopropoxydiacetylacetonate titanium with acetylacetonate iron, and then adding a first solvent to the resulting mixture to obtain the first mixture; wherein the volume ratio of the mixture to the first solvent can be 1:(14-18), for example, 1:14, 1:14.5, 1:15, 1:15.5, 1:16, 1:16.5, 1:17, 1:17.5, 1:18 or any combination thereof.

[0057] In addition, the first solvent may include n-butanol, specifically anhydrous n-butanol.

[0058] According to the inventors' research, in the above preparation process, diisopropoxy diacetylacetonate titanium, acetylacetonate iron and n-butanol are used, and a dense electron transport layer 21 doped with trivalent iron ions is prepared by dynamic spin coating. This is beneficial to further improve the conductivity and electron mobility of the dense electron transport layer 21, promote the charge transport between the electron transport layer 2 and the perovskite light-absorbing layer 3, enhance the fluorescence quenching effect, and thus further improve the photoelectric performance and efficiency of the perovskite solar cell.

[0059] In specific implementation, the organic titanium source and the iron source can be mixed in a glass bottle, and then a first solvent can be added and mixed evenly to obtain a first mixture. Then, the first mixture is coated on the transparent conductive layer 1. After coating, the film material on the second region 12 of the transparent conductive layer 1 is removed. Specifically, the film material on the second region 12 can be scraped off with a cotton swab soaked in isopropanol to expose the second region 12 of the transparent conductive layer 1. Subsequently, the transparent conductive layer 1 coated with the first mixture is placed on a flat heating table or other equipment for heating to perform the first drying treatment and form a dense electron transport layer 21.

[0060] S3. A second mixture containing an inorganic titanium source and a second solvent is coated onto the dense electron transport layer 21 to form a mesoporous electron transport layer 22.

[0061] Specifically, the second mixture can be spin-coated onto the dense electron transport layer 21 using a static spin-coating method. Specifically, the second mixture can be spin-coated onto the dense electron transport layer 21 at a rotation speed of 5500 to 6500 rpm (the rotation speed is, for example, 5500 rpm, 5700 rpm, 5900 rpm, 6000 rpm, 6200 rpm, 6400 rpm, 6500 rpm or any combination thereof). After a second drying treatment, a mesoporous electron transport layer 22 is formed.

[0062] Specifically, the second drying process may include an annealing process, with a temperature of 450 to 550°C, such as 450°C, 470°C, 490°C, 500°C, 520°C, 540°C, 550°C or any combination thereof, and a time of 40 to 70 minutes, such as 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes or any combination thereof.

[0063] In some embodiments, the second mixture is spin-coated onto the dense electron transport layer 21 using a static spin-coating method, and then annealed at 450–550°C for 40–70 min to form a mesoporous electron transport layer 22.

[0064] In specific implementation, the inorganic titanium source and the second solvent can be placed in a glass bottle and stirred thoroughly, for example, by adding a magnetic stirrer for magnetic stirring. The stirring time can be 20-30 hours, and the resulting mixed solution is the second mixture. Then, the second mixture is coated on the side of the dense electron transport layer 21 facing away from the transparent conductive layer 1. After coating, the film material on the second region 12 of the transparent conductive layer 1 is removed. Specifically, the film material on the second region 12 can be scraped off with a cotton swab soaked in isopropanol to expose the second region 12 of the transparent conductive layer 1. Subsequently, the entire substrate (including the transparent conductive layer 1, the dense electron transport layer 21 formed on the transparent conductive layer 1, and the second mixture coated on the dense electron transport layer 21) is placed on a flat heating table or other equipment for heating to perform a second drying process, forming a mesoporous electron transport layer 22.

[0065] Specifically, the inorganic titanium source mentioned above may include TiO2, which forms a mesoporous titanium dioxide layer (i.e., mesoporous titanium dioxide electron transport layer 2) through the above process.

[0066] In addition, the second solvent may include ethanol.

[0067] Furthermore, the mass ratio of the inorganic titanium source to the second solvent can be 1:(7 to 9), for example, 1:7, 1:7.5, 1:8, 1:8.5, 1:9 or any combination thereof.

[0068] S4. A perovskite light-absorbing layer 3 is formed on the mesoporous electron transport layer 22.

[0069] Specifically, the perovskite light-absorbing layer 3 is formed on the side of the mesoporous electron transport layer 22 facing away from the dense electron transport layer 21. In a specific implementation, the material used to form the perovskite light-absorbing layer 3 (such as the aforementioned metal halide and / or organic halide, etc.) can be mixed with a third solvent and stirred thoroughly (the stirring time can be 4 to 5 hours) to obtain a perovskite precursor solution. The perovskite precursor solution is spin-coated onto the mesoporous electron transport layer 22. Specifically, spin-coating can be performed at a rotation speed of 3500 to 4500 rpm (the rotation speed is, for example, 3500 rpm, 3700 rpm, 3900 rpm, 4000 rpm, 4200 rpm, 4400 rpm, 4500 rpm or any combination thereof). An anti-solvent is dropped onto the wet film formed on the mesoporous electron transport layer 22 (specifically, the anti-solvent can be dropped about 20 seconds before the end of spin-coating). After spin-coating, annealing is performed to form the perovskite light-absorbing layer 3.

[0070] The annealing process can include stepped annealing, which involves at least two annealing stages, with the annealing temperature and time increasing progressively, or the annealing time remaining approximately the same for each stage. By performing at least two annealing stages, annealing can be performed first at a lower temperature to slow solvent evaporation and grow larger perovskite grains, thereby optimizing the photoelectric effect of perovskite solar cells. Then, annealing can be performed at a higher temperature to thoroughly remove the solvent.

[0071] In some specific embodiments, the annealing process includes performing a first annealing process and a second annealing process in sequence. The temperature of the first annealing process can be 110-120°C and the time can be 3-5 min. The temperature of the second annealing process can be 140-160°C and the time can be 5-10 min. That is, after spin coating, the sample is annealed at 110-120°C for 3-5 min and then annealed at 140-160°C for 5-10 min to form a perovskite light-absorbing layer.

[0072] The third solvent may include dimethyl sulfoxide (DMSO) and / or dimethylformamide (DMF), preferably a mixture of DMSO and DMF, and the antisolvent may include diethyl ether.

[0073] S5. A hole transport layer 4 is formed on the perovskite light-absorbing layer 3.

[0074] Specifically, the hole transport layer 4 is formed on the side of the perovskite light-absorbing layer 3 facing away from the mesoporous electron transport layer 22. It can be formed by conventional methods in the art, such as spin coating. For example, Spiro-OMeTAD is spin coated on the perovskite light-absorbing layer 3 and oxidized for 10 to 14 hours to form the Spiro-OMeTAD hole transport layer 4.

[0075] After spin coating is completed, the film material on the second region 12 of the transparent conductive layer 1 is removed. Specifically, a cotton swab soaked in γ-hydroxybutyrate lactone (GBL) can be used to scrape off the film material on the second region 12 to expose the second region 12 of the transparent conductive layer 1.

[0076] S6: A counter electrode 5 is formed on the second region 12 of the transparent conductive layer 1 and the hole transport layer 4 to obtain a perovskite solar cell.

[0077] Specifically, the counter electrode 5 can be formed by vacuum evaporation, for example, by forming an Au electrode. In practice, conventional evaporation equipment in the field, such as a vacuum coating machine, can be used to perform vacuum evaporation to form the counter electrode 5, thereby obtaining the battery device (i.e., a perovskite solar cell).

[0078] The present invention will be further described below through specific embodiments and comparative examples.

[0079] Example 1

[0080] S1. Pretreatment of FTO conductive glass

[0081] The FTO conductive glass was ultrasonically cleaned sequentially with acetone, isopropanol, ethanol, and deionized water, with each cleaning session lasting 30 minutes.

[0082] Then the FTO conductive glass was placed in an oven and dried at 120°C;

[0083] The dried FTO conductive glass was subjected to ultraviolet ozone treatment for 30 minutes.

[0084] S2, Formation of the dense electron transport layer

[0085] Add acetylacetone iron to 2 mL of diisopropoxydiacetylacetone titanium (diisopropoxydiacetylacetone titanium from Alfa, 75% isopropanol solution) (the amount of acetylacetone iron added meets the molar ratio of iron to titanium shown in Table 1) to obtain mixed solution A (in mixed solution A, the molar ratio of acetylacetone iron to diisopropoxydiacetylacetone titanium is 1:75 (that is, the molar ratio of iron in acetylacetone iron to titanium in diisopropoxydiacetylacetone titanium is 1:75)).

[0086] Add 0.1 mL of mixed solution A to 0.7 mL of diisopropoxydiacetylacetonate titanium to obtain mixed solution B (in mixed solution B, the molar ratio of acetylacetonate iron to diisopropoxydiacetylacetonate titanium is 1:600).

[0087] Add 0.1 mL of mixed solution B to 1.6 mL of anhydrous n-butanol, shake well, and obtain the first mixed solution;

[0088] The first mixture was spin-coated onto FTO conductive glass at a speed of 2000 rpm using a dynamic spin-coating method, and then annealed at 120°C for 10 min to form a dense electron transport layer.

[0089] S3, Formation of the mesoporous electron transport layer

[0090] Titanium dioxide and anhydrous ethanol were mixed at a mass ratio of 1:8 and stirred for 12 hours to obtain a second mixture.

[0091] The second mixture was spin-coated onto the dense electron transport layer at a speed of 6000 rpm using a static spin-coating method, and then annealed at 500℃ for 50 min to form a mesoporous electron transport layer.

[0092] S4. Formation of the perovskite light-absorbing layer

[0093] Iodoformin, lead iodide, and chloromethylamine were placed in a mixed solvent of dimethyl sulfoxide and dimethylformamide and stirred for 6 hours to obtain a perovskite precursor solution.

[0094] The perovskite precursor solution was spin-coated onto the mesoporous electron transport layer at a speed of 4000 rpm. Diethyl ether (antisolvent) was added 20 s before the spin-coating was stopped. After spin-coating, the perovskite light-absorbing layer was first annealed at 120 °C for 5 min (first stage annealing) and then stepped annealed at 150 °C for 5 min (second stage annealing).

[0095] S5. Formation of the hole transport layer

[0096] Spiro-OMeTAD was spin-coated onto the perovskite light-absorbing layer and oxidized for 12 hours to form a hole transport layer.

[0097] S6. Formation of the counter electrode

[0098] A perovskite solar cell was fabricated by vacuum evaporation using a vacuum coating machine to form an Au electrode (counter electrode) on the side of the hole transport layer facing away from the perovskite light-absorbing layer and in the second region (the exposed conductive region) of the FTO conductive glass. Figure 4 Different batches of perovskite solar cells prepared according to the process of Example 1 are shown.

[0099] Comparative Example 1: The difference from Example 1 is that in step S2, 150 μL of diisopropoxydiacetylacetonate titanium and 2.4 mL of anhydrous n-butanol were mixed and shaken to obtain the first mixture (i.e., acetylacetonate iron was not added in step S2 of Comparative Example 1), and the other conditions were the same as in Example 1.

[0100] Examples 2 to 5: The difference from Example 1 is that the amount of iron acetylacetone used in step S2 is different (i.e. the content of trivalent iron compound in the formed dense electron transport layer is different), as shown in Table 1. Except for the differences shown in Table 1, the other conditions are the same as in Example 1.

[0101] Example 6: The difference from Example 1 is that the dense electron transport layer formed is not doped with ferric compounds, while the mesoporous electron transport layer is doped with ferric compounds. The difference in the preparation process is as follows:

[0102] (1) No acetylacetone iron is added in step S2 (i.e., 150 μL of diisopropoxydiacetylacetone titanium and 2.4 mL of anhydrous n-butanol are mixed and shaken to obtain the first mixture);

[0103] (2) Add acetylacetone iron in step S3 (that is, mix titanium dioxide and anhydrous ethanol in a mass ratio of 1:8 and then add acetylacetone iron to it;

[0104] The remaining conditions are the same as in Example 1.

[0105] The open-circuit voltage (Voc), current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of the perovskite solar cells in each embodiment and comparative example were measured as follows: Figure 1 As shown.

[0106] Table 1

[0107]

[0108] *: The amount of iron acetylacetone used in Table 1 is the molar ratio of iron to titanium (i.e., the molar ratio of iron acetylacetone to the titanium source used, calculated by iron and titanium elements).

[0109] As can be seen, compared with Comparative Example 1, the electron transport layer of Examples 1 to 7 introduces trivalent iron compounds, that is, the electron transport layer is doped with trivalent iron ions, which makes the perovskite solar cell have higher open circuit voltage, fill factor and energy conversion efficiency (photovoltaic conversion efficiency), thus improving the photoelectric performance and efficiency of the perovskite solar cell.

[0110] Among them, compared with Examples 2 and 5, the amount of iron acetylacetone used in Examples 1, 3 and 4 is within a more suitable range, which makes the dense electron transport layer doped with a more suitable amount of ferric ions, thereby making the perovskite solar cell exhibit better photoelectric performance and efficiency.

[0111] Compared to Example 6, Example 1 introduced a trivalent iron compound into the dense electron transport layer, exhibiting superior photoelectric performance and efficiency.

[0112] In addition, the steady-state photoluminescence spectra of the perovskite solar cells of Example 1 and Comparative Example 1 are shown below. Figure 2 The transient photoluminescence spectrum is shown below. Figure 3 This further illustrates that by introducing ferric compounds into the electron transport layer, thereby doping the electron transport layer with ferric ions, the photoelectric performance and efficiency of perovskite solar cells can be effectively improved.

[0113] In the description of this invention, terms such as "first" and "second" are used for descriptive purposes only, such as to distinguish between components to more clearly illustrate / explain the technical solution, and should not be construed as indicating or implying the number of technical features indicated or the order of features with substantial significance.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A perovskite solar cell, characterized in that, The device comprises a transparent conductive layer, an electron transport layer, a perovskite light-absorbing layer, and a hole transport layer stacked sequentially. The electron transport layer comprises titanium dioxide and ferric ions present in the titanium dioxide lattice in a doped form. The ferric ions are derived from a ferric compound, which is iron acetylacetonate. The electron transport layer includes a dense electron transport layer and a mesoporous electron transport layer located between the dense electron transport layer and the perovskite light-absorbing layer, wherein the trivalent iron compound is present in the dense electron transport layer; In the dense electron transport layer, the molar ratio of iron to titanium is 1:(300~650).

2. The perovskite solar cell according to claim 1, characterized in that, The transparent conductive layer includes FTO conductive glass.

3. A method for preparing a perovskite solar cell according to any one of claims 1-2, characterized in that, Includes the following steps: A first mixture containing an organic titanium source, an iron source for forming the trivalent iron compound, and a first solvent is coated onto a transparent conductive layer to form a dense electron transport layer. A second mixture containing an inorganic titanium source and a second solvent is coated onto the dense electron transport layer to form a mesoporous electron transport layer. A perovskite light-absorbing layer and a hole transport layer are sequentially formed on the mesoporous electron transport layer to obtain the perovskite solar cell.

4. The method for preparing a perovskite solar cell according to claim 3, characterized in that, Before applying the first mixture onto the transparent conductive layer, the transparent conductive layer is pretreated. The pretreatment process includes cleaning the transparent conductive layer with a cleaning agent, drying it, and then performing ultraviolet ozone treatment. The cleaning agent includes one or more of water, acetone, isopropanol, ethanol, and glass cleaner.

5. The method for preparing a perovskite solar cell according to claim 3, characterized in that, The organic titanium source includes titanium diisopropoxydiacetylacetone; And / or, the first solvent includes n-butanol.

6. The method for preparing a perovskite solar cell according to claim 3, characterized in that, The organic titanium source includes titanium diisopropoxybisacetylacetonate, and the iron source includes iron acetylacetonate. The process of forming the first mixture includes: mixing the titanium diisopropoxybisacetylacetonate with the iron acetylacetonate, and then adding a first solvent to the resulting mixture to obtain the first mixture; wherein the volume ratio of the mixture to the first solvent is 1:(14~18).

7. The method for preparing a perovskite solar cell according to any one of claims 3-6, characterized in that, The first mixture is spin-coated onto the transparent conductive layer using a dynamic spin-coating method, and then annealed at 110~130℃ for 8~12 minutes to form the dense electron transport layer.

8. The method for preparing a perovskite solar cell according to claim 4, characterized in that, The inorganic titanium source includes titanium dioxide; And / or, the second solvent includes ethanol; And / or, the second mixture is spin-coated onto the dense electron transport layer using a static spin-coating method, and then annealed at 450~550℃ for 40~70min to form the mesoporous electron transport layer.

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