Perovskite solar cell based on modified electron transport layer and preparation method thereof

Abstract

The invention provides a perovskite solar cell based on a modified electron transport layer and a preparation method thereof. The perovskite solar cell comprises a conductive substrate layer, an electron transport layer, a perovskite light absorption layer, a hole transport layer and a metal electrode layer which are stacked in sequence, wherein the electron transport layer comprises a cobalt complex and nano TiO2; the cobalt complex comprises a neutral NH3 ligand, and the valence state of cobalt in the cobalt complex is + 3; the molar ratio of the nano TiO2 to the cobalt complex is (8-12): 1. A cobalt complex with a specific molar weight is introduced into the electron transport layer of the perovskite solar cell, so that the energy level arrangement of nano TiO2 in the electron transport layer is improved, the cobalt complex interacts with defect sites in nano TiO2 crystal lattices, the defects are passivated, the conductivity of the electron transport layer is improved, non-radiative recombination at an interface is reduced, and the performance of the perovskite solar cell is improved. And finally, the open-circuit voltage and the overall efficiency of the perovskite solar cell are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of perovskite solar cells, and in particular to a perovskite solar cell based on a modified electron transport layer and a preparation method thereof. Background Art

[0002] Perovskite solar cells are single-junction solar cells that are made by stacking a perovskite halide crystal light-absorbing layer, a hole transport layer, and an electron transport layer to form a unidirectional transmission of photogenerated electrons and holes to the electron transport layer and the hole transport layer, respectively, and then to the metal collector to form a current. Perovskite solar cells have attracted widespread attention due to their high efficiency and low cost. In these cells, the electron transport layer (ETL) plays a vital role. It not only needs to effectively transport electrons from the perovskite layer to the external circuit, but also needs to block the reverse transmission of holes. TiO2, as a commonly used ETL material, has been widely studied due to its high electron mobility and good chemical stability. However, the energy level alignment between TiO2 and the perovskite layer is not always optimal, which limits the electron extraction efficiency and the performance of the entire solar cell.

[0003] Previous studies have explored various dopants, such as metal ions and organic compounds, to improve the performance of TiO2, hoping to enhance device performance by altering its electrical properties. However, these dopants can introduce additional defects or instabilities, affecting the long-term stability of solar cells.

[0004] Based on this, how to design the electron transport layer to effectively improve the electron mobility of the electron transport layer while ensuring its good compatibility with the perovskite light absorption layer, and ultimately make the corresponding solar cell have better performance, is a key technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The main purpose of the present invention is to provide a perovskite solar cell based on a modified electron transport layer and a preparation method thereof, so as to solve the problem in existing perovskite cells that the energy level alignment between the electron transport layer and the perovskite light absorbing layer is poor, resulting in poor electron extraction efficiency and poor performance of the corresponding solar cell.

[0006] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a perovskite solar cell based on a modified electron transport layer, the perovskite solar cell comprising a conductive substrate layer, an electron transport layer, a perovskite light absorption layer, a hole transport layer and a metal electrode layer stacked in sequence, the electron transport layer comprising a cobalt complex and nano-TiO2; the cobalt complex comprises a neutral NH3 ligand, and the valence state of cobalt in the cobalt complex is +3; the molar ratio of nano-TiO2 and the cobalt complex is (8 to 12):1.

[0007] Furthermore, the cobalt complex is selected from one or more of hexaamminecobalt(III) chloride, hexaamminecobalt(III) nitrate and pentaamminecobalt(III) chloride.

[0008] Furthermore, the D50 of nano-TiO2 is 10nm to 30nm, and the particle size span is 0.3 to 0.7.

[0009] Furthermore, the porosity of the electron transport layer is 5% to 20%, and the surface roughness is 1 nm to 5 nm.

[0010] Further, the thickness of the conductive substrate layer is 50nm~400nm, the thickness of the electron transport layer is 10nm~40nm, the thickness of the perovskite light absorption layer is 300nm~800nm, the thickness of the hole transport layer is 30nm~300nm, and the thickness of the metal electrode layer is 20nm~300nm; preferably, the thickness of the conductive substrate layer is 150nm~350nm, the thickness of the electron transport layer is 15nm~35nm, the thickness of the perovskite light absorption layer is 400nm~700nm, the thickness of the hole transport layer is 50nm~200nm, and the thickness of the metal electrode layer is 30nm~200nm; more preferably, the thickness of the conductive substrate layer is 200±20nm, the thickness of the electron transport layer is 15nm~25nm, the thickness of the perovskite light absorption layer is 500nm~600nm, the thickness of the hole transport layer is 80nm~120nm, and the thickness of the metal electrode layer is 80nm~150nm.

[0011] Furthermore, the conductive substrate layer is an FTO glass layer or an ITO glass layer; and / or the crystal chemical formula of the perovskite in the perovskite light absorbing layer is FA x MA 1-x PbI3, wherein x is 0.5 to 1.0; and / or, the hole transport layer is selected from one of a Spiro-oMeATD layer, a PTAA layer or a NiO layer, preferably a Spiro-oMeATD layer; and / or, the metal electrode layer is selected from one of a gold electrode layer, a silver electrode layer, a copper electrode layer or an amorphous carbon electrode layer, preferably a gold electrode layer.

[0012] The second aspect of the present invention provides a method for preparing the above-mentioned perovskite solar cell based on the modified electron transport layer, comprising: step S1, providing a conductive substrate layer; step S2, preparing a dispersion of nano-TiO2, adding a cobalt complex to the dispersion of nano-TiO2, and obtaining a modified dispersion by dispersion treatment; step S3, coating the modified dispersion on one side surface of the conductive substrate layer, and forming an electron transport layer on the surface of the conductive substrate layer after heat treatment; step S4, sequentially preparing a perovskite light absorption layer, a hole transport layer and a metal electrode layer on the side surface of the electron transport layer away from the conductive substrate layer to obtain a perovskite solar cell based on the modified electron transport layer.

[0013] Furthermore, in step S2, the concentration of the nano-TiO2 dispersion is 5 mg / mL to 15 mg / mL, preferably 10±2 mg / mL.

[0014] Furthermore, in step S2, the dispersion treatment includes stirring treatment and ultrasonic dispersion treatment performed in sequence; preferably, the stirring treatment time is 12±1h, and the stirring treatment is performed at 80±5°C.

[0015] Furthermore, in step S3, the heat treatment temperature is 150° C. to 200° C., and the time is 10 min to 30 min.

[0016] By applying the technical solution of the present invention, a specific molar amount of cobalt complex is introduced into the electron transport layer of the perovskite solar cell, thereby improving the energy level arrangement of the nano-TiO2 therein, and at the same time interacting with the defect sites in the nano-TiO2 lattice to passivate these defects, thereby improving the conductivity of the electron transport layer and reducing non-radiative recombination at the interface, thereby significantly improving the open circuit voltage and overall efficiency of the perovskite solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 A schematic structural diagram of a perovskite solar cell based on a modified electron transport layer provided by the present invention;

[0019] Figure 2 This is a curve showing the photoelectric conversion efficiency test results of the perovskite solar cell based on the modified electron transport layer obtained in Example 1 of the present invention;

[0020] Figure 3 This is a curve showing the photoelectric conversion efficiency test results of the perovskite solar cell obtained in Comparative Example 1 of the present invention.

[0021] The above drawings include the following reference numerals:

[0022] 10. Conductive substrate layer; 20. Electron transport layer; 30. Perovskite light absorption layer; 40. Hole transport layer; 50. Metal electrode layer. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0024] As described in the background art, in the prior art perovskite cell structure, the energy level alignment between the electron transport layer and the perovskite light absorbing layer is poor, which leads to the problems of poor electron extraction efficiency and poor cell performance. In order to solve the above technical problems, the first aspect of the present invention provides a perovskite solar cell based on a modified electron transport layer, such as Figure 1 As shown, the perovskite solar cell includes a conductive substrate layer 10, an electron transport layer 20, a perovskite light absorbing layer 30, a hole transport layer 40 and a metal electrode layer 50 stacked in sequence, wherein the electron transport layer 20 includes a cobalt complex and nano-TiO2; the cobalt complex includes a neutral NH3 ligand, and the valence state of cobalt in the cobalt complex is +3; the molar ratio of nano-TiO2 to the cobalt complex is (8-12):1.

[0025] The present invention provides nano-TiO2 modified with a specific cobalt complex in the electron transport layer 20. The addition of the cobalt complex greatly improves the performance of the electron transport layer, thereby enhancing the energy conversion efficiency and stability of the entire perovskite solar cell.

[0026] Specifically, Co 3+ It has a strong electron-accepting capacity, while the NH3 ligands can donate electrons. They can form coordination bonds with the hydroxyl groups rich in the TiO2 surface. Through the local transfer and redistribution of electrons, the Fermi level of TiO2 is improved, making it closer to the electronic energy level of the perovskite layer, thereby promoting rapid charge transfer, reducing electron-hole recombination, and increasing the open circuit voltage. At the same time, cobalt complexes with specific valence states and ligands can form stable chemical bonds with defect sites on the surface of TiO2 nanoparticles, passivating these sites and reducing non-radiative recombination paths, thereby improving the conductive efficiency and stability of the electron transport layer.

[0027] Furthermore, with respect to the microstructure of the electron transport layer 20, the TiO2 surface is negatively charged (-O － ), and [Co(NH3)6] 3+ Positively charged, it binds to the TiO2 surface through electrostatic adsorption, and this binding may be accompanied by hydrogen bond formation. 3+The introduction of may introduce an intermediate energy level near the conduction band of TiO2, reduce the electron transmission barrier, and move the Fermi level of TiO2 upward, closer to the conduction band of the perovskite layer.

[0028] In particular, compared to another ammonia ligand, NH2 － As a neutral molecule, the NH3 ligand will not significantly change the electronic structure of cobalt when forming a coordination bond with the metal cobalt center, thereby making the complex structure more stable, so as to more effectively optimize the energy level of TiO2 and improve the conductivity of the resulting electron transport layer. The Co(III) complex has a smaller dd transition energy gap than the Co(II) complex, which is conducive to the rapid transmission of electrons in the electron transport layer. At the same time, Co 3+ The redox stability of Co 2+ The higher the content of the modified electron transport layer, the less likely it is to undergo redox reactions, and the more stable the chemical state can be maintained, thereby effectively improving the long-term stability of the modified electron transport layer and the performance stability of the solar cell.

[0029] Furthermore, in order to provide a more superior electronic regulation and defect passivation effect for TiO2, thereby optimizing its performance in perovskite solar cells, the cobalt complex is preferably selected from one or more of hexaamminecobalt(III) chloride, hexaamminecobalt(III) nitrate, and pentaamminecobalt(III) chloride. In particular, when the cobalt complex is hexaamminecobalt(III) chloride, it has a stable hexacoordinated octahedral structure, in which the cobalt ion is surrounded by six ammonia molecules, forming a tight coordination environment, so as to provide a more stable chemical environment, reduce dissociation during the application process, and thus enable the photovoltaic conversion efficiency of the solar cell to be higher, while the performance is also more stable. － The ions may combine with the hydroxyl groups (-OH) on the TiO2 surface through ion exchange, releasing HCl and forming Ti-O-Co bonds, thereby reducing the defects on the surface of the transport layer.

[0030] In several preferred embodiments, the D50 of the nano-TiO2 is preferably 10nm to 30nm, more preferably 10nm to 20nm, to facilitate the formation of a denser electron transport layer and improve electron conduction efficiency. Furthermore, the particle size span is preferably 0.3 to 0.7, thereby reducing the size variation of the nano-TiO2 particles and, in turn, reducing the discontinuity of the interlayer interface of the electron transport layer, thereby improving the electron transport efficiency therein and the photoelectric conversion performance of the entire device.

[0031] In order to provide a more continuous electron transport path, reduce non-radiative recombination, reduce defects within the layer and on the surface of the layer, promote good contact with the perovskite layer, further reduce the charge transfer barrier at the interface, and ultimately more significantly improve the photoelectric conversion efficiency of the battery, the porosity of the electron transport layer 20 is preferably 5% to 20%, and the surface roughness is 1nm to 5nm.

[0032] In several preferred embodiments, the thickness of the conductive substrate layer 10 is 50nm to 400nm, the thickness of the electron transport layer 20 is 10nm to 40nm, the thickness of the perovskite light absorption layer 30 is 300nm to 800nm, the thickness of the hole transport layer 40 is 30nm to 300nm, and the thickness of the metal electrode layer 50 is 20nm to 300nm. In several more preferred embodiments, in order to more effectively improve the open circuit voltage and short circuit current density of the battery and ultimately improve the photoelectric conversion efficiency, the thickness ranges of each layer are further refined as follows: the thickness of the conductive substrate layer 10 is 150nm to 350nm, the thickness of the electron transport layer 20 is 15nm to 35nm, the thickness of the perovskite light absorption layer 30 is 400nm to 700nm, the thickness of the hole transport layer 40 is 50nm to 200nm, and the thickness of the metal electrode layer 50 is 30nm to 200nm. After extensive experiments, the inventors have found that in several particularly preferred embodiments, the thickness of the conductive substrate layer 10 is preferably 200±20nm, the thickness of the electron transport layer 20 is 15nm~25nm, the thickness of the perovskite light absorption layer 30 is 500nm~600nm, the thickness of the hole transport layer 40 is 80nm~120nm, and the thickness of the metal electrode layer 50 is 80nm~150nm. Among them, the more precise thickness control of the conductive substrate layer 10 and the electron transport layer 20 in coordination with each other can promote the efficient transfer of charges, reduce charge recombination at the interface, and at the same time improve the stability and reliability of the entire battery structure. The optimized thickness of the perovskite light absorption layer 30, the hole transport layer 40, and the metal electrode layer 50 not only more effectively ensures the full absorption of light, but also further optimizes the transfer and collection of charges, thereby more significantly improving the photoelectric conversion efficiency of the battery and reducing its energy loss.

[0033] Furthermore, in order to obtain a solar cell with better comprehensive performance, based on the composition and structure of the special modified electron transport layer provided by the present invention, it is preferred that the conductive substrate layer 10 is a FTO glass layer or an ITO glass layer; and / or the crystal chemical formula of the perovskite in the perovskite light absorbing layer 30 is FA x MA 1-xPbI3, wherein x is 0.5 to 1.0; and / or, the hole transport layer 40 is selected from one of a Spiro-oMeATD layer, a PTAA layer or a NiO layer, preferably a Spiro-oMeATD layer; and / or, the metal electrode layer 50 is selected from one of a gold electrode layer, a silver electrode layer, a copper electrode layer or an amorphous carbon electrode layer, preferably a silver electrode layer.

[0034] The second aspect of the present invention provides a method for preparing the above-mentioned perovskite solar cell based on the modified electron transport layer, comprising: step S1, providing a conductive substrate layer 10; step S2, preparing a dispersion of nano-TiO2, adding a cobalt complex to the dispersion of nano-TiO2, and obtaining a modified dispersion by dispersion treatment; step S3, coating the modified dispersion on one side surface of the conductive substrate layer 10, and forming an electron transport layer 20 on the surface of the conductive substrate layer 10 after heat treatment; step S4, sequentially preparing a perovskite light absorption layer 30, a hole transport layer 40 and a metal electrode layer 50 on the side surface of the electron transport layer 20 away from the conductive substrate layer 10, to obtain a perovskite solar cell based on the modified electron transport layer.

[0035] For the above-mentioned perovskite solar cell based on the modified electron transport layer, the present invention provides a preparation method thereof accordingly. By adding a specific cobalt complex to a dispersion of TiO2 nanoparticles, followed by coating and heat treatment, a modified electron transport layer (ETL) with a special structure is formed. The obtained modified TiO2 electron transport layer exhibits better energy level alignment characteristics, cooperates more closely with the perovskite layer, can reduce the occurrence of non-radiative recombination, and improves the extraction efficiency of electrons. At the same time, the heat treatment step in the above-mentioned preparation process ensures the crystallinity and stability of the TiO2 layer, further enhancing the performance of the electron transport layer.

[0036] In order to further optimize the film quality of the electron transport layer 20, the concentration of the nano-TiO2 dispersion in step S2 is preferably 5 mg / mL to 15 mg / mL. On this basis, because too high or too low a concentration may affect the uniformity and density of the film, and thus affect the electron transport efficiency, the concentration of the nano-TiO2 dispersion is further preferably 10±2 mg / mL, thereby forming a more uniform, dense, and microstructured electron transport layer 20 on the conductive substrate layer 10, and ultimately more effectively improving the overall performance of the perovskite solar cell based on the modified electron transport layer.

[0037] In several typical embodiments, the dispersion treatment in step S2 preferably includes stirring treatment and ultrasonic dispersion treatment performed in sequence. This refined dispersion treatment method can make the cobalt complex more evenly distributed in the TiO2 dispersion, reduce the uneven modification caused by local high concentration, and improve the stability of the modified dispersion, thereby further improving the conductivity and stability of the formed electron transport layer 10. The preferred stirring treatment time is 12±1h, and the stirring treatment is carried out at 80±5°C, which can more effectively promote the grafting between the cobalt complex and TiO2, improve the efficiency of the modification process and the stability of the obtained electron transport layer 20, a thin film product, thereby making the perovskite solar cell in which it is located more superior.

[0038] Furthermore, the temperature of the heat treatment in step S3 is preferably 150°C to 200°C, and the time is 10min to 30min. Within this temperature range, the cobalt complex can form a more stable structure with the TiO2 particles, similar to a coordination bond graft, that is, a more stable bond is formed, thereby forming a denser, more uniform electron transport layer that is more closely matched to the energy level of the perovskite light absorption layer. In addition, this preferred heat treatment temperature condition can also enhance the interface compatibility between the formed electron transport layer 20 and the subsequent perovskite light absorption layer 30, reduce interface defects, improve electron transport efficiency, and ultimately improve the photoelectric conversion efficiency and stability of the entire perovskite solar cell.

[0039] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0040] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0041] Example 1

[0042] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0043] (1) Preparation of an ITO glass substrate (i.e., a conductive base layer): A 200 nm thick ITO glass layer was deposited on a clean glass substrate by magnetron sputtering. The ITO glass layer was then cleaned sequentially with acetone, isopropyl alcohol, and deionized water to remove surface impurities and oil stains.

[0044] (2) Preparation of the slurry for the modified electron transport layer: Low-temperature TiO2 nanoparticles were prepared by a sol-gel method, with TiCl4 as the main raw material and ethanol as the dispersant, to obtain a TiO2 nanoparticle dispersion having a concentration of 10 mg / mL. Hexaamminecobalt(III) chloride (CAS No. 10534-89-1) was added to the dispersion at a molar ratio of 10:1 (nano-TiO2:hexaamminecobalt(III) chloride). The mixture was heated to 80°C and stirred for 12 hours. The mixture was then ultrasonically dispersed to obtain a modified TiO2 nanoparticle dispersion, i.e., a modified dispersion.

[0045] (3) Preparation of electron transport layer: A layer of TiO2 modified with hexaaminocobalt chloride was spin-coated on one side of the cleaned ITO glass layer. After heat treatment at 150°C for 30 min, an electron transport layer with a thickness of 25 nm was formed.

[0046] (4-1) Preparation of the perovskite light-absorbing layer: Weigh a certain amount of FAI, MACl, and PbI2 (the molar ratio of FAI, MACl, and PbI2 is 1.0:0.1:1) in a glass bottle, add a certain amount of DMF solvent, and stir until the solids are completely dissolved to form a perovskite precursor solution; spin-coat the precursor solution on the formed electron transport layer at a speed of 3000 rpm for 60 seconds. The resulting product is then placed on a heating table and annealed at 100°C to form a 600nm thick perovskite film, where the crystal chemical formula of the perovskite is FA x MA 1-x PbI3, where x = 0.9 to 0.98.

[0047] (4-2) Preparation of hole transport layer: Spiro-OMeTAD solution with a concentration of 72.3 mg / mL was dissolved in chlorobenzene (CB) and doped with 35 μL / mL of Li-TFSI solution (260 mg / ml, dissolved in acetonitrile) and 30 μL / mL of 4-tBP (to assist dissolution). After filtering, the Spiro-OMeTAD solution was spin-coated at 3000 rpm for 30 seconds on the formed perovskite layer without annealing to obtain a hole transport layer with a thickness of 100 nm. It should be noted that Spiro-OMeTAD needs to be oxidized to activate its hole transport ability. The spin-coated sample can be placed in a drying cabinet overnight to fully oxidize.

[0048] (4-3) Preparation of the Metal Electrode Layer: A layer of silver (Ag) was deposited on the hole transport layer by thermal evaporation to serve as the metal electrode. The thickness of the silver electrode was controlled to be 100 nm, and a perovskite solar cell based on the modified electron transport layer was finally obtained.

[0049] Example 2

[0050] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0051] (1) Preparation of an ITO glass substrate (i.e., a conductive base layer): A 150 nm thick ITO glass layer was deposited on a clean glass substrate by magnetron sputtering. The ITO glass layer was cleaned sequentially with acetone, isopropyl alcohol, and deionized water to remove surface impurities and oil stains.

[0052] (2) Preparation of the slurry for the modified electron transport layer: Low-temperature TiO2 nanoparticles were prepared by a sol-gel method, with TiCl4 as the main raw material and water as the dispersant, to obtain a TiO2 nanoparticle dispersion having a concentration of 15 mg / mL. Hexaamminecobalt(III) nitrate (CAS No. 10534-86-8) was added to the dispersion at a molar ratio of 8:1 (nano-TiO2:hexaamminecobalt(III) nitrate), heated to 85°C and stirred for 5 hours, followed by ultrasonic dispersion to obtain a modified TiO2 nanoparticle dispersion, i.e., a modified dispersion.

[0053] (3) Preparation of electron transport layer: A layer of TiO2 modified with hexaaminocobalt chloride was spin-coated on one side of the cleaned ITO glass layer. After heat treatment at 150°C for 20 min, an electron transport layer with a thickness of 35 nm was formed.

[0054] (4-1) Preparation of the perovskite light-absorbing layer: Weigh a certain amount of FAI, MACl, and PbI2 (the molar ratio of FAI, MACl, and PbI2 is 1.0:0.1:1) in a glass bottle, add a certain amount of DMF solvent, and stir until the solids are completely dissolved to form a perovskite precursor solution; spin-coat the precursor solution on the formed electron transport layer at a speed of 4000 rpm for 40 seconds. The resulting product is then placed on a heating table and annealed at 150°C to form a 700nm thick perovskite film, where the crystal chemical formula of the perovskite is FA x MA 1-x PbI3, where x = 0.9 to 0.95.

[0055] (4-2) Preparation of hole transport layer: Spiro-OMeTAD solution with a concentration of 72.3 mg / mL was dissolved in chlorobenzene (CB) and doped with 35 μL / mL of Li-TFSI solution (260 mg / ml, dissolved in acetonitrile) and 30 μL / mL of 4-tBP (to assist dissolution). After filtering, the Spiro-OMeTAD solution was spin-coated at 3000 rpm for 40 seconds on the formed perovskite layer without annealing to obtain a hole transport layer with a thickness of 200 nm. It should be noted that Spiro-OMeTAD needs to be oxidized to activate its hole transport ability. The spin-coated sample can be placed in a drying cabinet overnight to fully oxidize.

[0056] (4-3) Preparation of the Metal Electrode Layer: A layer of silver (Ag) was deposited on the hole transport layer by thermal evaporation to serve as the metal electrode. The thickness of the silver electrode was controlled to be 200 nm, and a perovskite solar cell based on the modified electron transport layer was finally obtained.

[0057] Example 3

[0058] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0059] (1) Preparation of an ITO glass substrate (conductive base layer): A 350 nm thick ITO glass layer was deposited on a clean glass substrate by magnetron sputtering. The ITO glass layer was then cleaned sequentially with acetone, isopropyl alcohol, and deionized water to remove surface impurities and oil stains.

[0060] (2) Preparation of the slurry for the modified electron transport layer: Low-temperature TiO2 nanoparticles were prepared by a sol-gel method using TiCl4 as the main raw material and ethanol as the dispersant to obtain a TiO2 nanoparticle dispersion having a concentration of 5 mg / mL. Pentaamminecobalt(III) chloride (CAS No. 13859-51-3) was added to the dispersion at a molar ratio of 12:1 (nano-TiO2:pentaamminecobalt(III) chloride). The mixture was heated to 75°C and stirred for 13 hours. The mixture was then ultrasonically dispersed to obtain a modified TiO2 nanoparticle dispersion, i.e., a modified dispersion.

[0061] (3) Preparation of electron transport layer: A layer of TiO2 modified with hexaaminocobalt chloride was spin-coated on one side of the cleaned ITO glass layer. After heat treatment at 200°C for 30 min, an electron transport layer with a thickness of 25 nm was formed.

[0062] (4-1) Preparation of the perovskite light-absorbing layer: Weigh a certain amount of FAI, MACl, and PbI2 (the molar ratio of FAI, MACl, and PbI2 is 1.0:0.1:1) in a glass bottle, add a certain amount of DMF solvent, and stir until the solids are completely dissolved to form a perovskite precursor solution; spin-coat the precursor solution on the formed electron transport layer at a speed of 5000 rpm for 30 seconds. The resulting product is then placed on a heating table and annealed at 80°C to form a 400nm thick perovskite film, where the crystal chemical formula of the perovskite is FA x MA 1-x PbI3, where x = 0.9 to 0.98.

[0063] (4-2) Preparation of hole transport layer: Spiro-OMeTAD solution with a concentration of 72.3 mg / mL was dissolved in chlorobenzene (CB) and doped with 35 μL / mL of Li-TFSI solution (260 mg / ml, dissolved in acetonitrile) and 30 μL / mL of 4-tBP (to assist dissolution). After filtering, the Spiro-OMeTAD solution was spin-coated on the formed perovskite layer at 3000 rpm for 10 seconds without annealing to obtain a hole transport layer with a thickness of 50 nm. It should be noted that Spiro-OMeTAD needs to be oxidized to activate its hole transport ability. The spin-coated sample can be placed in a drying cabinet overnight to fully oxidize.

[0064] (4-3) Preparation of the Metal Electrode Layer: A layer of silver (Ag) was deposited on the hole transport layer by thermal evaporation to serve as the metal electrode. The thickness of the silver electrode was controlled to be 50 nm, and a perovskite solar cell based on the modified electron transport layer was finally obtained.

[0065] Example 4

[0066] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0067] The only difference between this embodiment and embodiment 1 is that the particle size of nano-TiO2 in the electron transport layer is different, see Table 1 for details.

[0068] Example 5

[0069] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0070] The only difference between this embodiment and embodiment 1 is that in step (2), the concentration of the TiO2 nanoparticle dispersion is changed to 20 mg / mL, and the stirring time is changed to 5 h and the temperature is changed to 90°C.

[0071] Example 6

[0072] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0073] The only difference between this embodiment and embodiment 1 is that in step (2), the concentration of the TiO2 nanoparticle dispersion is changed to 5 mg / mL, and the stirring time is changed to 20 h and the temperature is changed to 50°C.

[0074] Example 7

[0075] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0076] The only difference between this embodiment and embodiment 1 is that in step (3), the heat treatment temperature is changed to 250°C.

[0077] Example 8

[0078] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0079] The only difference between this embodiment and embodiment 1 is that in step (3), the heat treatment temperature is changed to 60°C.

[0080] Example 9

[0081] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0082] The only difference between this embodiment and embodiment 1 is that the thickness of each layer is different. Specifically, the thickness of the conductive base layer is 50 nm, the thickness of the electron transport layer is 10 nm, the thickness of the perovskite light absorption layer is 300 nm, the thickness of the hole transport layer is 30 nm, and the thickness of the metal electrode layer is 20 nm.

[0083] Example 10

[0084] A structure such as Figure 1 Preparation of perovskite solar cells based on modified electron transport layers as shown:

[0085] The only difference between this embodiment and embodiment 1 is that the thickness of each layer is different. Specifically, the thickness of the conductive base layer is 400 nm, the thickness of the electron transport layer is 40 nm, the thickness of the perovskite light absorption layer is 800 nm, the thickness of the hole transport layer is 300 nm, and the thickness of the metal electrode layer is 300 nm.

[0086] Comparative Example 1

[0087] Preparation of a perovskite solar cell:

[0088] The only difference between this comparative example and Example 1 is that in step (2), hexaamminecobalt(III) chloride is not added to the TiO2 nanoparticle dispersion.

[0089] Comparative Example 2

[0090] Preparation of a perovskite solar cell:

[0091] The only difference between this comparative example and Example 1 is that in step (2), the molar ratio of nano-TiO2 and hexaamminecobalt(III) chloride is adjusted to 5:1.

[0092] Comparative Example 3

[0093] Preparation of a perovskite solar cell:

[0094] The only difference between this comparative example and Example 1 is that in step (2), the molar ratio of nano-TiO2 and hexaamminecobalt (III) chloride is adjusted to 15:1.

[0095] Comparative Example 4

[0096] Preparation of a perovskite solar cell:

[0097] The difference between this comparative example and Example 1 is that in step (2), an equimolar amount of tetraamminecobalt(III) nitric acid carbonate (CAS No. 15040-52-5, wherein the ammonia ligand is NH2 － ) instead of hexaamminecobalt(III) chloride.

[0098] Comparative Example 5

[0099] Preparation of a perovskite solar cell:

[0100] The only difference between this comparative example and Example 1 is that in step (2), an equimolar amount of tetrakis-p-chlorophenylporphyrin cobalt (II) (CAS No. 55915-17-8) is used instead of hexaamminecobalt (III) chloride.

[0101] Test Method

[0102] D50 and particle size span ((D90-D10) / D50) of nano-TiO2 in the electron transport layer: obtained according to GB / T 26035-2010 test.

[0103] Porosity of the electron transport layer: measured by air adsorption method, the data is an estimated value.

[0104] Surface roughness of the electron transport layer: The surface roughness is measured using an atomic force microscope (AFM), and its value represents the root mean square value of the surface height difference of the electron transport layer.

[0105] Performance test of perovskite solar cells: Under room temperature, using a 3A solar simulator, at 100mW / cm 2 The photoelectric conversion efficiency of the perovskite solar cells prepared in each embodiment and comparative example was tested under a light intensity of , and the effective area of ​​the tested perovskite solar cell samples was 0.0049 cm 2 .

[0106] The above test results are shown in Table 1. And the test result curve of the perovskite solar cell based on the modified electron transport layer obtained in Example 1 is shown in Table 1. Figure 2 The test result curve of the perovskite solar cell obtained in comparative example 1 is shown in FIG. Figure 3 .

[0107] Table 1

[0108]

[0109] From the above description, it can be seen that the above-mentioned embodiment of the present invention greatly improves the performance of the electron transport layer by providing nano-TiO2 modified with a specific cobalt complex in the electron transport layer, thereby improving the energy conversion efficiency and stability of the entire perovskite solar cell.

[0110] More specifically, by comparing Example 2 and Example 3 with Example 1, it can be seen that the preferred cobalt complex is hexaamminecobalt (III) chloride, and the thickness of each layer is correspondingly preferred, which can make the photoelectric conversion efficiency of the solar cell higher and the performance more stable.

[0111] Comparing Example 4 with Example 1, it can be seen that the D50 of the nano-TiO2 is preferably 10 nm to 30 nm, which can form a denser electron transport layer in the obtained solar cell and improve its electron conduction efficiency.

[0112] Comparing Example 5 and Example 6 with Example 1, it can be seen that the concentration of the nano-TiO2 dispersion in step S2 is preferably 5 mg / mL to 15 mg / mL, and the stirring time is preferably 12±1h, and the stirring treatment is carried out at 80±5°C, which can promote the formation of a more uniform, dense, and microstructurally ideal electron transport layer on the conductive substrate layer, and ultimately more effectively improve the overall performance of the perovskite solar cell based on the modified electron transport layer.

[0113] Comparing Example 7 and Example 8 with Example 1, it can be seen that the temperature of the heat treatment in step S3 is preferably 150°C to 200°C, which can form a denser and more uniform electron transport layer that is more closely matched to the energy level of the perovskite light absorption layer, and ultimately improve the photoelectric conversion efficiency and stability of the entire perovskite solar cell.

[0114] Comparing Examples 9, 10, 2, and 3 with Example 1, it can be seen that by gradually optimizing the thickness of each layer, efficient charge transfer can be promoted, charge recombination at the interface can be reduced, and the stability and reliability of the entire battery structure can be improved. At the same time, sufficient light absorption is more effectively ensured, and charge transfer and collection are further optimized, thereby significantly improving the battery's photoelectric conversion efficiency and reducing its energy loss.

[0115] Comparing Comparative Examples 1 to 5 with Example 1, it can be seen that by introducing a cobalt complex into the electron transport layer and controlling the molar ratio of nano-TiO2 and the cobalt complex to (8 to 12): 1, the performance of the electron transport layer can be greatly improved, thereby improving the energy conversion efficiency and stability of the entire perovskite solar cell.

[0116] It should be noted that the terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0117] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A perovskite solar cell based on a modified electron transport layer, the perovskite solar cell comprising a conductive substrate layer (10), an electron transport layer (20), a perovskite light absorbing layer (30), a hole transport layer (40) and a metal electrode layer (50) stacked in sequence, characterized in that: The electron transport layer (20) includes a cobalt complex and nano-TiO2; The cobalt complex includes a neutral NH3 ligand, and the valence state of cobalt in the cobalt complex is +3; The molar ratio of the nano-TiO2 to the cobalt complex is (8-12):

1.

2. The perovskite solar cell based on a modified electron transport layer according to claim 1, characterized in that The cobalt complex is selected from one or more of hexaamminecobalt(III) chloride, hexaamminecobalt(III) nitrate and pentaamminecobalt(III) chloride.

3. The perovskite solar cell based on a modified electron transport layer according to claim 1 or 2, characterized in that: The D50 of the nano-TiO2 is 10nm-30nm, and the particle size span is 0.3-0.

7.

4. The perovskite solar cell based on a modified electron transport layer according to any one of claims 1 to 3, characterized in that The porosity of the electron transport layer (20) is 5% to 20%, and the surface roughness is 1 nm to 5 nm.

5. The perovskite solar cell based on a modified electron transport layer according to any one of claims 1 to 4, characterized in that The thickness of the conductive substrate layer (10) is 50 nm to 400 nm, the thickness of the electron transport layer (20) is 10 nm to 40 nm, the thickness of the perovskite light absorption layer (30) is 300 nm to 800 nm, the thickness of the hole transport layer (40) is 30 nm to 300 nm, and the thickness of the metal electrode layer (50) is 20 nm to 300 nm; Preferably, the thickness of the conductive substrate layer (10) is 150 nm to 350 nm, the thickness of the electron transport layer (20) is 15 nm to 35 nm, the thickness of the perovskite light absorption layer (30) is 400 nm to 700 nm, the thickness of the hole transport layer (40) is 50 nm to 200 nm, and the thickness of the metal electrode layer (50) is 30 nm to 200 nm; More preferably, the thickness of the conductive substrate layer (10) is 200±20 nm, the thickness of the electron transport layer (20) is 15 nm to 25 nm, the thickness of the perovskite light absorption layer (30) is 500 nm to 600 nm, the thickness of the hole transport layer (40) is 80 nm to 120 nm, and the thickness of the metal electrode layer (50) is 80 nm to 150 nm.

6. The perovskite solar cell based on a modified electron transport layer according to any one of claims 1 to 5, characterized in that The conductive substrate layer (10) is an FTO glass layer or an ITO glass layer; and / or, The crystal chemical formula of the perovskite in the perovskite light absorbing layer (30) is FA x MA 1-x PbI3, wherein x is 0.5 to 1.0; and / or, The hole transport layer (40) is selected from one of a Spiro-oMeATD layer, a PTAA layer or a NiO layer, preferably the Spiro-oMeATD layer; and / or, The metal electrode layer (50) is selected from one of a gold electrode layer, a silver electrode layer, a copper electrode layer or an amorphous carbon electrode layer, and is preferably the silver electrode layer.

7. A method for preparing a perovskite solar cell based on a modified electron transport layer according to any one of claims 1 to 6, characterized in that: include: Step S1, providing the conductive base layer (10); Step S2, preparing a nano-TiO2 dispersion, adding a cobalt complex to the nano-TiO2 dispersion, and performing a dispersion treatment to obtain a modified dispersion; Step S3, coating the modified dispersion on one side surface of the conductive base layer (10), and forming the electron transport layer (20) on the surface of the conductive base layer (10) after heat treatment; Step S4, sequentially preparing the perovskite light absorbing layer (30), the hole transport layer (40) and the metal electrode layer (50) on the surface of the electron transport layer (20) away from the conductive substrate layer (10) to obtain the perovskite solar cell based on the modified electron transport layer.

8. The method for preparing a perovskite solar cell based on a modified electron transport layer according to claim 7, characterized in that: In step S2, the concentration of the nano-TiO2 dispersion is 5 mg / mL to 15 mg / mL, preferably 10±2 mg / mL.

9. The method for preparing a perovskite solar cell based on a modified electron transport layer according to claim 7 or 8, characterized in that: In step S2, the dispersion process includes stirring and ultrasonic dispersion process performed sequentially; Preferably, the stirring treatment is carried out for 12±1 h and at a temperature of 80±5°C.

10. The method for preparing a perovskite solar cell based on a modified electron transport layer according to any one of claims 7 to 9, characterized in that: In step S3, the heat treatment temperature is 150° C. to 200° C., and the time is 10 min to 30 min.

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