A carbon back electrode, a preparation method thereof, and a perovskite solar cell assembled from the carbon back electrode

Abstract

The present invention belongs to the technical field of solar cells, and provides a carbon back electrode, a preparation method thereof, and a perovskite solar cell assembled from the carbon back electrode. An ammonium transition metal chalcogenide, an emulsifier, water and a monomer are mixed to obtain a mixed solution; an initiator aqueous solution and the mixed solution are subjected to a polymerization reaction, and the resulting product is subjected to carbonization treatment to obtain carbon nanospheres; the nanospheres, other carbon materials, carbon black, a binder and a solvent are mixed to obtain a carbon paste; a tin dioxide precursor solution is coated on a substrate, and an electron transport layer is formed after annealing; a PbX2 solution is coated on the electron transport layer, and a PbX2 thin film is formed after annealing; an AY solution is coated on the PbX2 thin film, and a perovskite thin film is obtained after annealing; the carbon paste is deposited on the perovskite thin film, and a back electrode is obtained after heating and curing, and a perovskite solar cell is assembled. The obtained cell has very excellent open circuit voltage, short circuit current density, fill factor and photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a carbon back electrode, a preparation method thereof, and a perovskite solar cell assembled from the carbon back electrode. Background Art

[0002] With the rapid development of the global economy, the consumption of energy by people is increasing day by day. Especially, the overuse of traditional fossil fuels has caused serious environmental and energy crises. In order to cope with the serious greenhouse effect caused by the excessive emission of global carbon dioxide, countries are constantly increasing the development and utilization of renewable energy. China has put forward the energy development and utilization solutions of "carbon peak" and "carbon neutrality". Compared with other renewable energies, solar energy has the advantages of rich reserves and wide distribution. Therefore, in the future energy structure, solar energy and its derived photovoltaic industry will occupy a very important position. Among many solar photovoltaic cells, perovskite solar cells have become a rising star in the photovoltaic field due to their low cost, simple preparation process, high photoelectric conversion efficiency and other characteristics.

[0003] After more than a decade of development, perovskite solar cells have achieved remarkable breakthroughs, and their photoelectric conversion efficiency has reached 25.7%, which is comparable to that of commercially available silicon solar cells. Although the development of perovskite solar cells is very rapid, they also face a series of problems and challenges. At present, the most studied perovskite solar cell structure is the formal n-i-p type of FTO / electron transport layer / perovskite layer / hole transport layer / back electrode. The most commonly used hole transport layer materials are Spiro-OMeTAD, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), etc. They are highly sensitive to the environment and easy to absorb moisture, resulting in poor stability of perovskite solar cells, which restricts their industrial application. In addition, the back electrode mostly uses noble metal materials such as gold and silver. These noble metals are easy to react with the halogen ions with migration effect in perovskite, causing the degradation of perovskite and further reducing the stability of the battery. In addition, these hole transport layer, noble metal electrode and other materials are all expensive. The noble metal electrode usually also uses the preparation processes of magnetron sputtering or vacuum evaporation, with complex operation processes and high energy consumption, which also increases the cost of the device to a certain extent and becomes another factor restricting the commercialization of perovskite solar cells.

[0004] To solve the problems of poor stability and high cost caused by the hole transport layer and noble metal electrodes, carbon-based perovskite solar cells with carbon materials as the back electrode have attracted the attention of researchers. The carbon back electrode has the dual functions of hole extraction and electron collection, simplifies the battery structure, reduces costs, and improves the battery stability. Carbon materials have excellent electrical conductivity and ductility, simple preparation processes, easy processing, etc., and have a work function similar to that of gold and silver electrodes, and are considered to be the most suitable alternative noble metal perovskite solar cell back electrode materials. Compared with organic hole transport layers and noble metal electrodes, carbon materials have stable chemical properties and hydrophobic characteristics, significantly improving the environmental stability of carbon-based perovskite solar cells. However, carbon materials have low selectivity for holes and poor hole extraction ability; at the same time, the work function of carbon materials differs greatly from the valence band energy level of perovskite, resulting in interfacial energy level mismatch and serious energy loss; in addition, the contact between the perovskite layer / carbon electrode interface is poor, and there are a large number of defect states on the perovskite surface, leading to serious charge recombination and reducing charge transport and extraction. These adverse factors make the photovoltaic performance of carbon-based perovskite solar cells quite different from that of traditional-structured solar cells. Therefore, designing and preparing multifunctional carbon electrode materials with high hole extraction rate, energy level matching, and improved interfacial properties has important theoretical significance and practical value for improving the photovoltaic performance of carbon-based perovskite solar cells. Summary of the Invention

[0005] The purpose of the present invention is to provide a carbon back electrode, a preparation method thereof, and a perovskite solar cell assembled from the carbon back electrode to make up for the deficiencies of the prior art.

[0006] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of a carbon back electrode, comprising the following steps:

[0008] (1) Mix an ammonium transition metal chalcogenate, an emulsifier, water, and a monomer to obtain a mixed solution;

[0009] (2) Mix an aqueous initiator solution and the mixed solution obtained in step (1), and carry out a polymerization reaction. The generated product is subjected to carbonization treatment to obtain heteroatom-rich carbon nanospheres composite with a transition metal chalcogenide;

[0010] (3) Mix the heteroatom-rich carbon nanospheres composite with a transition metal chalcogenide obtained in step (2), other carbon materials, carbon black, a binder, and a solvent to obtain a carbon paste;

[0011] The other carbon materials include one or more of carbon nanotubes, graphite, and carbon fibers;

[0012] (4) Coating the preheated tin dioxide precursor solution onto a substrate, and annealing to form a tin dioxide electron transport layer;

[0013] (5) Coating the PbX2 solution onto the tin dioxide electron transport layer, and annealing to form a PbX2 thin film; wherein, X includes I, Br or Cl;

[0014] (6) Coating the AY solution onto the PbX2 thin film, and annealing to obtain a perovskite thin film; wherein, A includes a formamidine group, a methylamine group or Cs, and Y includes I, Br or Cl;

[0015] (7) Depositing the carbon paste obtained in step (3) onto the perovskite thin film obtained in step (6), and heating and curing to obtain a carbon back electrode;

[0016] There is no limitation on the sequence of steps (1)-(3) and steps (4)-(6).

[0017] Preferably, the emulsifier in step (1) includes one or more of TX-100, P135 and F127, and the dosage ratio of the emulsifier to water is 1-2 mg:1 mL;

[0018] The monomer includes one or more of aniline, pyrrole, and thiophene, and the volume concentration of the monomer in the mixed solution is 1-2%;

[0019] The ammonium transition metal chalcogenate includes one or more of ammonium tetrathiotungstate, ammonium tetrathiomolybdate, ammonium molybdate, ammonium paratungstate, ammonium copper sulfate and ammonium nickel sulfate, and the molar percentage of the ammonium transition metal chalcogenate in the monomer is 0-2%, and the dosage of the ammonium transition metal chalcogenate is not zero.

[0020] Preferably, the initiator in step (2) includes one or more of ammonium persulfate, potassium persulfate and sodium persulfate, and the concentration of the initiator aqueous solution is 0.05-0.2 g / mL;

[0021] The initiator aqueous solution and the mixed solution obtained in step (1) are refrigerated and then mixed. The refrigeration temperature is independently 0-5°C, and the refrigeration time is independently 30-60 min;

[0022] The volume ratio of the initiator aqueous solution to the water in step (1) is 15-25:55-65;

[0023] The temperature of the polymerization reaction is 0-5°C, and the time is 24-48 h;

[0024] The temperature of the carbonization treatment is 700-1200°C, and the time is 3-6 h. The carbonization treatment is carried out under a protective atmosphere.

[0025] Preferably, in step (3), the mass ratio of the transition metal chalcogenide - composite heteroatom - rich carbon nanospheres, other carbon materials, and carbon black is 5 - 7:2 - 3:1 - 2, and the mass ratio of the carbon materials, binder, and solvent is 2 - 3:0.5 - 1:7 - 8. The carbon materials refer to the sum of the transition metal chalcogenide - composite heteroatom - rich carbon nanospheres, other carbon materials, and carbon black;

[0026] The solvent includes one or more of terpineol, ethyl acetate, and chlorobenzene;

[0027] The binder includes one or more of cellulose - based binders, acetate - based binders, titanate - based binders, and acrylate - based binders.

[0028] Preferably, in step (4), the pre - heating temperature is 50 - 90 °C and the time is 0.5 - 1.5 h;

[0029] The tin dioxide precursor solution is prepared from stannous chloride, thiourea, and water, and the dosage ratio of stannous chloride, thiourea, and water is 830 - 870 mg:310 - 360 mg:20 - 40 mL;

[0030] The coating is spin - coating, the spin - coating speed is 1500 - 2500 revolutions per minute, and the spin - coating time is 20 - 40 seconds;

[0031] The annealing temperature is 150 - 250 °C and the time is 0.5 - 2 h.

[0032] Preferably, in step (5), the concentration of the PbX2 solution is 0.8 - 1.8 mol / L, and the solvent includes N,N - dimethylformamide or dimethyl sulfoxide;

[0033] The coating is spin - coating, the spin - coating speed is 6000 - 8000 revolutions per minute, and the spin - coating time is 20 - 40 seconds;

[0034] The annealing temperature is 70 - 100 °C and the time is 0.5 - 2 h.

[0035] Preferably, in step (6), the concentration of the AY solution is 0.06 - 1.5 mol / L, and the solvent includes isopropanol or methanol;

[0036] The coating is spin - coating, the spin - coating speed is 6000 - 8000 revolutions per minute, and the spin - coating time is 20 - 40 seconds;

[0037] The annealing temperature is 90 - 250 °C and the time is 0.5 - 2 h.

[0038] Preferably, in step (7), the temperature for heat - curing is 50 - 100 °C and the time is 1 - 1.5 h;

[0039] The thickness of the obtained back electrode is 10 - 20 μm.

[0040] The present invention also provides a carbon back electrode obtained by the above method.

[0041] The present invention also provides a perovskite solar cell assembled from the carbon back electrode, and the perovskite solar cell is a perovskite solar cell based on a polymer-derived heteroatom-doped carbon in-situ composite transition metal chalcogenide back electrode;

[0042] The open-circuit voltage of the perovskite solar cell is 1.45 - 1.65 V, the short-circuit current density is 6.5 - 8.0 mA·cm -2 , the fill factor is 0.70 - 0.85, and the photoelectric conversion efficiency is 7.50 - 10.50%.

[0043] Advantages of the present invention:

[0044] 1. The present invention uses a polymer-derived carbon nanosphere in-situ composite transition metal chalcogenide as the back electrode of a perovskite solar cell, which has many advantages: (1) The present invention uses a polymer nanosphere-transition metal chalcogenide raw material as a precursor, and in-situ composites the transition metal chalcogenide on the surface of the polymer-derived carbon nanosphere through a one-step pyrolysis method, which simplifies the material preparation process and optimizes the properties of the carbon material; (2) The inherent nitrogen and sulfur elements in the polymer-derived carbon nanospheres have lone pairs of electrons, which can bind to the incompletely coordinated cations on the surface of the perovskite, improve the interfacial contact between the perovskite layer and the carbon electrode, passivate the defect states, and improve the charge transport and extraction; at the same time, the in-situ composite of nitrogen and sulfur elements can also improve the conductivity of the carbon nanospheres and regulate their work functions; (3) The in-situ composite of a p-type transition metal chalcogenide with a high hole mobility is beneficial to reducing the resistance of the composite carbon nanospheres, improving the conductivity and hole extraction ability of the carbon back electrode, reducing the work function of the carbon electrode, effectively regulating the energy level matching between the perovskite layer and the back electrode, promoting the extraction of carriers and reducing energy loss.

[0045] 2. The preparation process adopted by the present invention is simple, the material cost is low, and large-scale processing equipment is not required, which solves the problem of high cost of noble metal back electrodes and hole transport layers. The prepared carbon electrode has the dual functions of hole extraction and electron collection, simplifies the battery structure, and improves the stability. The preparation technology adopted can adjust the structure of the polymer nanospheres by using different ratios of various monomers, and then regulate the elemental composition of the carbon nanospheres generated by carbonization. Moreover, different transition metal chalcogenide composite nanocarbon spheres can be prepared by an in-situ composite process to obtain a new type of carbon back electrode with excellent hole conduction ability and adjustable energy bands. The carbon electrode material has great room for improvement, good repeatability and expandability, and has strong commercial potential and application prospects.

[0046] 3. The photovoltaic performance of the unencapsulated novel carbon-based all-inorganic CsPbBr3 perovskite solar cell assembled by the present invention is significantly improved, and it exhibits excellent stability. After operating for 720 hours under air conditions with 85% relative humidity, the efficiency of the battery can still be maintained above 90% of the initial value. Brief Description of the Drawings

[0047] Figure 1 It is a scanning electron microscope image of 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention.

[0048] Figure 2 It is a scanning electron microscope image of a novel carbon back electrode prepared by using 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention.

[0049] Figure 3 It is the X-ray photoelectron spectrum of 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention.

[0050] Figure 4 It is the J-V curve of perovskite solar cells with N-doped carbon nanospheres composite with various transition metal chalcogenides provided by the present invention and carbon nanospheres of the comparative example as the back electrode.

[0051] Figure 5 It is the stability diagram of perovskite solar cells with 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention and carbon nanospheres of the comparative example as the back electrode. Detailed Description of the Invention

[0052] The present invention provides a preparation method of a carbon back electrode, which comprises the following steps:

[0053] (1) Mix an ammonium salt of a transition metal chalcogenide, an emulsifier, water and a monomer to obtain a mixed solution;

[0054] (2) Mix an aqueous initiator solution and the mixed solution obtained in step (1), and carry out a polymerization reaction. The generated product is subjected to carbonization treatment to obtain transition metal chalcogenide composite heteroatom-rich carbon nanospheres;

[0055] (3) Mix the transition metal chalcogenide composite heteroatom-rich carbon nanospheres obtained in step (2), other carbon materials, carbon black, a binder and a solvent to obtain a carbon paste;

[0056] The other carbon materials include one or more of carbon nanotubes, graphite and carbon fibers;

[0057] (4) Coat a preheated tin dioxide precursor solution on a substrate, and form a tin dioxide electron transport layer after annealing;

[0058] (5) Coating a PbX2 solution on the tin dioxide electron transport layer, and annealing to form a PbX2 thin film; wherein, X includes I, Br or Cl;

[0059] (6) Coating an AY solution on the PbX2 thin film, and annealing to obtain a perovskite thin film; wherein, A includes a formamidine group, a methylamine group or Cs, and Y includes I, Br or Cl;

[0060] (7) Depositing the carbon paste obtained in step (3) on the perovskite thin film obtained in step (6), and heating and curing to obtain a carbon back electrode;

[0061] There is no limitation on the order of steps (1)-(3) and steps (4)-(6).

[0062] In the present invention, the emulsifier described in step (1) includes one or more of TX-100, P135 and F127, and the dosage ratio of the emulsifier to water is 1-2 mg:1 mL, preferably 1.2-1.8 mg:1 mL, and more preferably 1.4-1.6 mg:1 mL;

[0063] The monomer includes one or more of aniline, pyrrole, and thiophene, and the volume concentration of the monomer in the mixed solution is 1-2%, preferably 1.2-1.8%, and more preferably 1.4-1.6%;

[0064] The ammonium transition metal chalcogenide includes one or more of ammonium tetrathiotungstate, ammonium tetrathiomolybdate, ammonium molybdate, ammonium paratungstate, ammonium copper sulfate hexahydrate and ammonium nickel sulfate hexahydrate. The molar percentage of the ammonium transition metal chalcogenide in the monomer is 0-2%, preferably 0.5-1.5%, and more preferably 1-1.2%; and the dosage of the ammonium transition metal chalcogenide is not zero.

[0065] Step (1) of the present invention is preferably carried out under sealed conditions for mixing, which can prevent the interference of pollutants in the air.

[0066] In the present invention, the initiator described in step (2) includes one or more of ammonium persulfate, potassium persulfate and sodium persulfate, and the concentration of the initiator aqueous solution is 0.05-0.2 g / mL, preferably 0.1-0.15 g / mL, and more preferably 0.12-0.13 g / mL;

[0067] The initiator aqueous solution and the mixed solution obtained in step (1) are refrigerated and then mixed. The refrigeration temperature is independently 0-5°C, preferably 1-4°C, and more preferably 2-3°C; the refrigeration time is independently 30-60 min, preferably 40-50 min, and more preferably 45-46 min;

[0068] The volume ratio of the initiator aqueous solution to the water in step (1) is 15-25:55-65, preferably 20-22:58-60;

[0069] The temperature of the polymerization reaction is 0-5 °C, preferably 1-4 °C, more preferably 2-3 °C; the time is 24-48 h, preferably 30-45 h, more preferably 35-40 h;

[0070] The temperature of the carbonization treatment is 700-1200 °C, preferably 800-1100 °C, more preferably 900-1000 °C; the time is 3-6 h, preferably 4-5 h; the carbonization treatment is carried out under a protective atmosphere, preferably a nitrogen atmosphere.

[0071] After the polymerization reaction in step (2) of the present invention is completed, the product system is filtered by suction, washed and then dried, and then carbonized; the drying time is 12-24 h, preferably 15-20 h, and the drying temperature is preferably 90-110 °C, more preferably 100-105 °C.

[0072] The heating rate to the carbonization treatment temperature in step (2) of the present invention is 15-25 °C / min, preferably 20-22 °C / min.

[0073] The transition metal chalcogenide generated in step (2) of the present invention is: MoS x 、WS x 、MoO x 、WO x 、CuO x 、NiO x (x = 1-3, specifically 1, 2 or 3, etc.).

[0074] Refrigeration in step (2) of the present invention can reduce the solution temperature, reduce the polymerization reaction rate during the dropping process, and make the reaction more complete.

[0075] In the present invention, the mass ratio of the transition metal chalcogenide-composite heteroatom-rich carbon nanospheres, other carbon materials and carbon black in step (3) is 5-7:2-3:1-2, preferably 6:2-2.5:1-1.5; the mass ratio of the carbon materials, binder and solvent is 2-3:0.5-1:7-8, preferably 2.5-2.8:0.6-0.8:7.3-7.8; the carbon materials refer to the sum of the transition metal chalcogenide-composite heteroatom-rich carbon nanospheres, other carbon materials and carbon black;

[0076] The solvent includes one or more of terpineol, ethyl acetate and chlorobenzene;

[0077] The binder includes one or more of a cellulose binder, an acetate binder, a titanate binder, and an acrylate binder, and specifically may be one or more of ethyl cellulose, isopropyl titanate, and polymethyl methacrylate. When using isopropyl titanate in the present invention, glacial acetic acid is preferably added simultaneously. The combination of isopropyl titanate and glacial acetic acid generates a complex with a Ti-O-Ti structure, increasing the binding effect of the binder; the mass ratio of isopropyl titanate to glacial acetic acid is 30-35:3-10, preferably 32-33:6-7.

[0078] In step (3) of the present invention, the mixing is ball milling, and the rotation speed of the ball milling is 400-600 revolutions per minute, preferably 500-550 revolutions per minute; the time of the ball milling is 8-12 h, preferably 10 h.

[0079] In the present invention, in step (4), the temperature of the preheating is 50-90 °C, preferably 60-80 °C, more preferably 70-75 °C; the time is 0.5-1.5 h, preferably 0.8-1.2 h, more preferably 1 h;

[0080] The tin dioxide precursor solution is prepared from stannous chloride, thiourea, and water. Specifically, stannous chloride, thiourea, and water are mixed at room temperature and stirred for 30-40 h, preferably 36-38 h. After centrifuging the product, the supernatant is retained to obtain it; the dosage ratio of stannous chloride, thiourea, and water is 830-870 mg:310-360 mg:20-40 mL, preferably 840-860 mg:330-350 mg:25-30 mL;

[0081] The coating is spin coating, and the speed of the spin coating is 1500-2500 revolutions per minute, preferably 1800-2000 revolutions per minute; the time of the spin coating is 20-40 seconds, preferably 30-35 seconds;

[0082] The temperature of the annealing is 150-250 °C, preferably 180-220 °C, more preferably 200-210 °C; the time is 0.5-2 h, preferably 1-1.5 h.

[0083] The substrate in step (4) of the present invention is preferably an FTO glass substrate.

[0084] In the present invention, in step (5), the concentration of the PbX2 solution is 0.8-1.8 mol / L, preferably 1-1.5 mol / L, more preferably 1.2-1.3 mol / L; the solvent includes N,N-dimethylformamide or dimethyl sulfoxide;

[0085] The coating is spin coating, and the spin coating speed is 6000 - 8000 revolutions per minute, preferably 6500 - 7000 revolutions per minute; the spin coating time is 20 - 40 seconds, preferably 30 - 35 seconds;

[0086] The annealing temperature is 70 - 100 °C, preferably 80 - 90 °C, and the time is 0.5 - 2 h, preferably 1 - 1.5 h.

[0087] In the present invention, in step (6), the concentration of the AY solution is 0.06 - 1.5 mol / L, preferably 0.5 - 1 mol / L; the solvent contains isopropanol or methanol;

[0088] The coating is spin coating, and the spin coating speed is 6000 - 8000 revolutions per minute, preferably 6500 - 7000 revolutions per minute; the spin coating time is 20 - 40 seconds, preferably 30 - 35 seconds;

[0089] The annealing temperature is 90 - 250 °C, preferably 120 - 220 °C, and more preferably 150 - 200 °C; the time is 0.5 - 2 h, preferably 1 - 1.5 h.

[0090] In the present invention, in step (7), the temperature for heat curing is 50 - 100 °C, preferably 60 - 90 °C, and more preferably 70 - 80 °C; the time is 1 - 1.5 h, preferably 1.2 - 1.4 h;

[0091] The thickness of the obtained back electrode is 10 - 20 μm, preferably 12 - 16 μm.

[0092] The present invention also provides a carbon back electrode obtained by the above method.

[0093] The present invention also provides a perovskite solar cell assembled with the carbon back electrode. The perovskite solar cell is a perovskite solar cell based on a polymer-derived heteroatom-doped carbon in-situ composite transition metal chalcogenide back electrode;

[0094] The open circuit voltage of the perovskite solar cell is 1.45 - 1.65 V, the short circuit current density is 6.5 - 8.0 mA·cm -2 , the fill factor is 0.70 - 0.85, and the photoelectric conversion efficiency is 7.50 - 10.50%.

[0095] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0096] Example 1

[0097] 1. Under the action of a magnetic stirrer at 600 revolutions per minute, 0.1 g of TX-100 emulsifier was added dropwise to 60 mL of deionized water at a rate of 1 drop per minute. Then, 10.5 mg of ammonium tetrathiomolybdate was added to the above solution. After stirring evenly, 290 μL of pyrrole and 380 μL of aniline were added dropwise to the mixed solution at a rate of 30 seconds per drop, and the mixture was sealed and stirred at room temperature for 30 minutes, followed by sonication for 30 minutes. 20 mL of an aqueous solution of ammonium persulfate with a concentration of 0.1 g / mol was prepared. The sonicated mixed solution and the ammonium persulfate aqueous solution were both refrigerated at 0 °C for 30 minutes. The ammonium persulfate aqueous solution was added dropwise to the mixed solution at a rate of 0.4 mL / min, and polymerization was carried out at 0 °C for 24 hours. Subsequently, the polymerized solution was filtered by suction, washed, and then dried in a vacuum at 100 °C for 12 hours. The dried product was added to a tube furnace, and under nitrogen protection, it was heated to 900 °C at a heating rate of 20 °C per minute and maintained for 4 hours, and then cooled to room temperature to obtain 0.5% MoS2 composite N-doped carbon nanospheres;

[0098] 2. 70 mg of MoS2 composite carbon nanospheres, 20 mg of carbon nanotubes, and 10 mg of carbon black were respectively added to 400 mg of terpineol. The above-obtained substances were ball-milled for 2 hours, then 30 mg of ethyl cellulose was added, and then ball-milling was continued for 10 hours at a ball-milling speed of 500 revolutions per minute to obtain a novel carbon paste;

[0099] 3. 853 mg of stannous chloride and 338 mg of thiourea were added to 30 mL of deionized water, and the mixture was continuously stirred at room temperature for 36 hours. After centrifuging the product, the supernatant was retained to obtain a tin dioxide precursor solution. The tin dioxide precursor solution was preheated at 90 °C for 30 minutes, and the tin dioxide precursor solution was spin-coated on the surface-treated FTO glass substrate (2000 revolutions per minute, 30 seconds), and annealed at 200 °C for 1 hour to form a dense tin dioxide electron transport layer;

[0100] 4. 2.97 g of lead bromide powder was added to 8 mL of DMF (N-N dimethylformamide), and it was dissolved on a heating platform at 90 °C to prepare a DMF solution of lead bromide with a concentration of 1 mol / L. 1.48 g of cesium bromide powder was added to a 100 mL volumetric flask, and after volume-fixing with anhydrous methanol, it was sonicated to obtain a methanol solution of cesium bromide with a concentration of 0.07 mol / L;

[0101] 5. The DMF solution of lead bromide was preheated at 90 °C for 30 minutes, and 90 μL was taken and spin-coated on the film prepared in step 4 (2000 revolutions per minute, 30 seconds), and then annealed at 90 °C for 30 minutes to obtain a lead bromide film;

[0102] 6. Spin-coat a cesium bromide methanol solution (2000 revolutions per minute, 30 seconds) on the lead bromide film prepared in step 5, heat and anneal at 250 °C for 5 minutes, spin-coat again after cooling, and repeat this operation 8 times to obtain a high-quality CsPbBr3 perovskite layer;

[0103] 7. Knife-coat the carbon paste obtained in step 2 on the surface of the CsPbBr3 perovskite film obtained in step 6, heat and cure at 50 °C for 1 hour to obtain the back electrode, and assemble a perovskite solar cell with an FTO / tin dioxide electron transport layer / CsPbBr3 perovskite layer / novel carbon back electrode structure.

[0104] Example 2

[0105] 1. Under the action of a magnetic stirrer at 600 revolutions per minute, add 0.1 g of TX-100 emulsifier dropwise to 60 mL of deionized water at a rate of 1 drop per minute, then add 21 mg of ammonium tetrathiomolybdate to the above solution, stir evenly, and then add 290 μL of pyrrole and 380 μL of aniline dropwise to the mixed solution at a rate of 30 seconds per drop, and seal and stir at room temperature for 30 minutes, followed by ultrasonic treatment for 30 minutes; prepare 20 mL of an aqueous solution of ammonium persulfate at 0.1 g / mol, and refrigerate the ultrasonicated mixed solution and the aqueous solution of ammonium persulfate at 0 °C for 30 minutes; add the aqueous solution of ammonium persulfate dropwise to the mixed solution at a rate of 0.4 mL / min, polymerize at 0 °C for 24 hours, then filter the polymerized solution, wash it, and dry it in a vacuum at 100 °C for 12 hours; add the dried product to a tube furnace, heat it to 900 °C at a heating rate of 20 °C per minute under nitrogen protection and hold for 4 hours, and then cool it to room temperature to obtain 1% MoS2 composite N-doped carbon nanospheres by carbonization;

[0106] 2. Add 70 mg of MoS2 composite carbon nanospheres, 20 mg of carbon nanotubes, and 10 mg of carbon black to 400 mg of terpineol respectively, ball-mill the above obtained substances for 2 hours, then add 30 mg of ethyl cellulose, and then continue to ball-mill for 10 hours at a ball-milling speed of 500 revolutions per minute to prepare a novel carbon paste;

[0107] 3. Add 853 mg of stannous chloride and 338 mg of thiourea to 30 mL of deionized water, continuously stir at room temperature for 36 hours, centrifuge the product and retain the supernatant to obtain a tin dioxide precursor solution. Preheat the tin dioxide precursor solution at 90 °C for 30 minutes, spin-coat the tin dioxide precursor solution (2000 revolutions per minute, 30 seconds) on the surface-treated FTO glass substrate, and anneal at 200 °C for 1 hour to form a dense tin dioxide electron transport layer;

[0108] 4. Add 2.97 g of lead bromide powder to 8 mL of DMF (N-N dimethylformamide), and dissolve it on a heating table at 90 °C to prepare a 1 mol / L lead bromide DMF solution. Add 1.48 g of cesium bromide powder to a 100 mL volumetric flask, make up the volume with anhydrous methanol, and then ultrasonicate to prepare a 0.07 mol / L cesium bromide methanol solution;

[0109] 5. Preheat the lead bromide DMF solution at 90 °C for 30 minutes, take 90 μL and spin-coat it on the film prepared in step 4 (2000 rpm, 30 s), and then anneal it at 90 °C for 30 minutes to obtain a lead bromide film;

[0110] 6. Spin-coat the cesium bromide methanol solution on the lead bromide film prepared in step 5 (2000 rpm, 30 s), heat and anneal it at 250 °C for 5 minutes, cool it, and then spin-coat it again. Repeat this operation 8 times to obtain a high-quality CsPbBr3 perovskite layer;

[0111] 7. Knife-coat the carbon paste obtained in step 2 on the surface of the CsPbBr3 perovskite film obtained in step 6, heat and cure it at 50 °C for 1 hour to obtain a back electrode, and assemble it into a perovskite solar cell with an FTO / tin dioxide electron transport layer / CsPbBr3 perovskite layer / novel carbon back electrode structure.

[0112] Example 3

[0113] 1. Under the action of a magnetic stirrer at 600 rpm, add 0.1 g of TX-100 emulsifier dropwise to 60 mL of deionized water at a rate of 1 drop per minute, then add 42.5 mg of ammonium tetrathiomolybdate to the above solution, stir well, and then add 290 μL of pyrrole and 380 μL of aniline dropwise to the mixed solution at a rate of 30 seconds per drop, and seal and stir at room temperature for 30 minutes, and then ultrasonicate for 30 minutes; Prepare 20 mL of an aqueous solution of ammonium persulfate at 0.1 g / mol, and refrigerate the ultrasonically treated mixed solution and the aqueous solution of ammonium persulfate at 0 °C for 30 minutes; Add the aqueous solution of ammonium persulfate dropwise to the mixed solution at a rate of 0.4 mL / min, polymerize at 0 °C for 24 hours, then filter the polymerized solution, wash it, and dry it in vacuo at 100 °C for 12 hours; Add the dried product to a tube furnace, heat it to 900 °C at a heating rate of 20 °C per minute under nitrogen protection and hold for 4 hours, and then cool it to room temperature to obtain 2% MoS2 composite N-doped carbon nanospheres by carbonization;

[0114] 2. Add 70 mg of MoS2 composite carbon nanospheres, 20 mg of carbon nanotubes, and 10 mg of carbon black to 400 mg of terpineol respectively. Ball-mill the above obtained product for 2 hours, then add 30 mg of ethyl cellulose, and then continue to ball-mill for 10 hours at a ball-mill speed of 500 rpm to prepare a novel carbon paste;

[0115] 3. Add 853 mg of stannous chloride and 338 mg of thiourea to 30 mL of deionized water, continuously stir for 36 hours at room temperature, centrifuge the product, and retain the supernatant to obtain a tin dioxide precursor solution. Preheat the tin dioxide precursor solution at 90 °C for 30 minutes, spin-coat the tin dioxide precursor solution on the surface-treated FTO glass substrate (2000 rpm, 30 s), and anneal at 200 °C for 1 hour to form a dense tin dioxide electron transport layer;

[0116] 4. Add 2.97 g of lead bromide powder to 8 mL of DMF (N,N-dimethylformamide), dissolve it on a heating platform at 90 °C to prepare a 1 mol / L lead bromide DMF solution. Add 1.48 g of cesium bromide powder to a 100 mL volumetric flask, make up the volume with anhydrous methanol, and ultrasonicate to obtain a 0.07 mol / L cesium bromide methanol solution;

[0117] 5. Preheat the lead bromide DMF solution at 90 °C for 30 minutes, take 90 μL and spin-coat it on the film prepared in step 4 (2000 rpm, 30 s), and then anneal at 90 °C for 30 minutes to obtain a lead bromide film;

[0118] 6. Spin-coat the cesium bromide methanol solution on the lead bromide film prepared in step 5 (2000 rpm, 30 s), heat and anneal at 250 °C for 5 minutes, cool down and spin-coat again, repeat this operation 8 times to obtain a high-quality CsPbBr3 perovskite layer;

[0119] 7. Knife-coat the carbon paste obtained in step 2 on the surface of the CsPbBr3 perovskite film obtained in step 6, heat and cure at 50 °C for 1 hour to obtain a back electrode, and assemble a perovskite solar cell with an FTO / tin dioxide electron transport layer / CsPbBr3 perovskite layer / novel carbon back electrode structure.

[0120] Example 4

[0121] 1. Under the action of a magnetic stirrer at 600 revolutions per minute, 0.1 g of TX-100 emulsifier was added dropwise to 60 mL of deionized water at a rate of 1 drop per minute. Then, 32.3 mg of ammonium copper sulfate hexahydrate was added to the above solution. After stirring evenly, 290 μL of pyrrole and 380 μL of aniline were added dropwise to the mixed solution at a rate of 30 seconds per drop, and the mixture was sealed and stirred at room temperature for 30 minutes, followed by ultrasonic treatment for 30 minutes. 20 mL of an ammonium persulfate aqueous solution with a concentration of 0.1 g / mol was prepared. The ultrasonicated mixed solution and the ammonium persulfate aqueous solution were both refrigerated at 0 °C for 30 minutes. The ammonium persulfate aqueous solution was added dropwise to the mixed solution at a rate of 0.4 mL / min, and polymerization was carried out at 0 °C for 24 hours. Subsequently, the polymerized solution was filtered by suction, washed, and then dried in vacuo at 100 °C for 12 hours. The dried product was added to a tube furnace, heated to 900 °C at a heating rate of 20 °C per minute under nitrogen protection, and maintained for 4 hours, and then cooled to room temperature to obtain 1% CuO₂ composite N-doped carbon nanospheres by carbonization;

[0122] 2. 60 mg of CuO₂ composite carbon nanospheres, 30 mg of graphite, and 10 mg of carbon black were respectively added to 400 mg of terpineol. The above-obtained substances were ball-milled for 2 hours, then 32 mg of isopropyl titanate and 6 mg of glacial acetic acid were added, and then ball-milling was continued for 10 hours at a ball-milling speed of 500 revolutions per minute to prepare a novel carbon slurry;

[0123] 3. 853 mg of stannous chloride and 338 mg of thiourea were added to 30 mL of deionized water, and the mixture was continuously stirred at room temperature for 36 hours. After centrifuging the product, the supernatant was retained to obtain a tin dioxide precursor solution. The tin dioxide precursor solution was preheated at 90 °C for 30 minutes, and the tin dioxide precursor solution was spin-coated on the surface-treated FTO glass substrate (2000 revolutions per minute, 30 seconds), and annealed at 200 °C for 1 hour to form a dense tin dioxide electron transport layer;

[0124] 4. 2.97 g of lead bromide powder was added to 8 mL of DMF (N-N dimethylformamide), and it was dissolved on a heating table at 90 °C to prepare a DMF solution of lead bromide with a concentration of 1 mol / L. 1.48 g of cesium bromide powder was added to a 100 mL volumetric flask, fixed with anhydrous methanol, and then ultrasonicated to prepare a cesium bromide methanol solution with a concentration of 0.07 mol / L;

[0125] 5. The DMF solution of lead bromide was preheated at 90 °C for 30 minutes, and 90 μL was taken and spin-coated on the film prepared in step 4 (2000 revolutions per minute, 30 seconds), and then annealed at 90 °C for 30 minutes to obtain a lead bromide film;

[0126] 6. Spin-coat a cesium bromide methanol solution (2000 revolutions per minute, 30 seconds) on the lead bromide film prepared in step 5, heat-anneal it at 250 °C for 5 minutes, spin-coat again after cooling, and repeat this operation 8 times to obtain a high-quality CsPbBr3 perovskite layer;

[0127] 7. Knife-coat the carbon paste obtained in step 2 on the surface of the CsPbBr3 perovskite film obtained in step 6, heat-cure it at 50 °C for 1 hour to obtain the back electrode, and assemble it into a perovskite solar cell with an FTO / tin dioxide electron transport layer / CsPbBr3 perovskite layer / novel carbon back electrode structure.

[0128] Example 5

[0129] 1. Under the action of a magnetic stirrer at 600 revolutions per minute, add 0.1 g of TX-100 emulsifier dropwise to 60 mL of deionized water at a rate of 1 drop per minute, then add 28.1 mg of ammonium tetrathiomolybdate to the above solution, stir evenly, and then add 290 μL of pyrrole and 380 μL of aniline dropwise to the mixed solution at a rate of 1 drop per 30 seconds, and seal and stir at room temperature for 30 minutes, followed by sonication for 30 minutes; Prepare 20 mL of an aqueous solution of ammonium persulfate with a concentration of 0.1 g / mol, and refrigerate both the sonicated mixed solution and the ammonium persulfate aqueous solution at 0 °C for 30 minutes; Add the ammonium persulfate aqueous solution dropwise to the mixed solution at a rate of 0.4 mL / min, polymerize at 0 °C for 24 hours, then filter the polymerized solution by suction, wash it, and dry it in vacuo at 100 °C for 12 hours; Add the dried product to a tube furnace, heat it up to 900 °C at a heating rate of 20 °C per minute under nitrogen protection and hold for 4 hours, and then cool it to room temperature to obtain 1% WS2 composite N-doped carbon nanospheres by carbonization;

[0130] 2. Add 60 mg of WS2 composite carbon nanospheres, 30 mg of graphite, and 10 mg of carbon black to 400 mg of terpineol respectively, ball-mill the above-obtained product for 2 hours, then add 32 mg of titanium isopropoxide and 6 mg of glacial acetic acid, and then continue to ball-mill for 10 hours at a ball-milling speed of 500 revolutions per minute to prepare a novel carbon paste;

[0131] 3. Add 853 mg of stannous chloride and 338 mg of thiourea to 30 mL of deionized water, continuously stir at room temperature for 36 hours, centrifuge the product and retain the supernatant to obtain a tin dioxide precursor solution. Preheat the tin dioxide precursor solution at 90 °C for 30 minutes, spin-coat the tin dioxide precursor solution (2000 revolutions per minute, 30 seconds) on the surface-treated FTO glass substrate, and anneal at 200 °C for 1 hour to form a dense tin dioxide electron transport layer;

[0132] 4. Add 2.97 grams of lead bromide powder to 8 milliliters of DMF (N-N dimethylformamide), and dissolve it on a heating table at 90 °C to prepare a DMF solution of lead bromide with a concentration of 1 mol / L. Add 1.48 grams of cesium bromide powder to a 100-milliliter volumetric flask, make up the volume with anhydrous methanol, and then ultrasonicate to prepare a methanol solution of cesium bromide with a concentration of 0.07 mol / L;

[0133] 5. Preheat the DMF solution of lead bromide at 90 °C for 30 minutes, take 90 microliters and spin-coat it on the film prepared in step 4 (2000 revolutions per minute, 30 seconds), and then anneal it at 90 °C for 30 minutes to obtain a lead bromide film;

[0134] 6. Spin-coat the methanol solution of cesium bromide on the lead bromide film prepared in step 5 (2000 revolutions per minute, 30 seconds), heat and anneal it at 250 °C for 5 minutes, cool it, and then spin-coat it again. Repeat this operation 8 times to obtain a high-quality CsPbBr3 perovskite layer;

[0135] 7. Knife-coat the carbon paste obtained in step 2 on the surface of the CsPbBr3 perovskite film obtained in step 6, heat and cure it at 50 °C for 1 hour to obtain a back electrode, and assemble it into a perovskite solar cell with an FTO / tin dioxide electron transport layer / CsPbBr3 perovskite layer / novel carbon back electrode structure.

[0136] The products obtained in each example were tested, and the results are as Figures 1 to 5 shown.

[0137] Figure 1 is the scanning electron microscope image of the 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention. It can be clearly seen from Figure 1 that the polymer-derived N-doped carbon nanospheres retain a very regular spherical structure. The diameter of the carbon nanospheres is about 80 - 120 nanometers. The in-situ composite preparation process does not damage their structure. The spherical structure is conducive to the uniform distribution of MoS2. The inherent N in the carbon nanospheres can combine with the cations that are not fully coordinated on the perovskite surface, improve the interfacial contact between the perovskite layer and the carbon electrode, passivate the ionic defect states, and improve the charge transport and extraction.

[0138] Figure 2 is the scanning electron microscope image of the novel carbon back electrode prepared using 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention. It can be seen from the figure that the carbon nanospheres are uniformly mixed with carbon nanotubes and carbon black. Their synergistic effect makes the inside of the carbon back electrode tightly combined, can form a good conductive path, and improves the conductivity of the carbon back electrode.

[0139] Figure 3X-ray photoelectron spectroscopy of the 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention. The appearance of the Mo element and S element peaks proves the successful composite of MoS2 with the carbon nanospheres. The in-situ composite of MoS2 with high hole mobility is beneficial to reducing the resistance of the composite carbon nanospheres, improving the conductivity and hole extraction ability of the carbon back electrode, reducing the work function of the carbon electrode, effectively adjusting the energy level matching between the perovskite layer and the back electrode, promoting the extraction of carriers and reducing the energy loss.

[0140] Figure 4 J-V curves of perovskite solar cells with N-doped carbon nanospheres composite with various transition metal chalcogenides provided by the present invention and carbon nanospheres of the comparative example as the back electrode. Compared with the polymer-derived pure carbon nanospheres, using N-doped carbon nanospheres composite with different types and different concentrations of transition metal chalcogenides as the back electrode of perovskite solar cells can significantly improve the photovoltaic performance of the devices.

[0141] Figure 5 Stability diagram of perovskite solar cells with the 1% MoS2 composite N-doped carbon nanospheres provided in Example 2 of the present invention and carbon nanospheres of the comparative example as the back electrode. As Figure 5 can be seen, after the cell with 1% MoS2 composite N-doped carbon nanospheres as the back electrode operates for 720 hours under the air condition of 85% relative humidity, the efficiency can still remain above 90% of the initial value, showing excellent stability.

[0142] The performance test results of the perovskite solar cells are as Figure 4 、 5 shown. Through the above method, a perovskite solar cell based on a polymer-derived heteroatom-doped carbon in-situ composite transition metal chalcogenide back electrode with an open-circuit voltage of 1.45 - 1.65 V, a short-circuit current density of 6.5 - 8.0 mA·cm -2 , a fill factor of 0.70 - 0.85, and a photoelectric conversion efficiency of 7.50% - 10.50% is obtained. After the cell operates for 720 hours under the air condition of 85% relative humidity, the efficiency can still remain above 90% of the initial value, showing excellent stability.

[0143] Comparative example

[0144] 1. Under the action of a magnetic stirrer at 600 revolutions per minute, 0.1 g of TX-100 emulsifier was dropped into 60 mL of deionized water at a rate of 1 drop per minute. After stirring evenly, 290 μL of pyrrole and 380 μL of aniline were dropped into the mixed solution at a rate of 1 drop per 30 seconds, and the mixture was sealed and stirred at room temperature for 30 minutes, followed by sonication for 30 minutes. 20 mL of an aqueous solution of ammonium persulfate with a concentration of 0.1 g / mol was prepared. The sonicated mixed solution and the ammonium persulfate aqueous solution were both refrigerated at 0 °C for 30 minutes. The ammonium persulfate aqueous solution was dropped into the mixed solution at a rate of 0.4 mL / min, and polymerization was carried out at 0 °C for 24 hours. Subsequently, the polymerized solution was filtered by suction, washed, and then dried in a vacuum at 100 °C for 12 hours. The dried product was added to a tubular furnace, heated to 900 °C at a heating rate of 20 °C per minute under nitrogen protection, and maintained for 4 hours, and then cooled to room temperature to obtain N-doped carbon nanospheres by carbonization;

[0145] 2. 70 mg of carbon nanospheres, 20 mg of carbon nanotubes, and 10 mg of carbon black were respectively added to 400 mg of terpineol. The above-obtained product was ball-milled for 2 hours, then 50 mg of ethyl cellulose was added, and then ball-milled for another 10 hours at a ball-milling speed of 500 revolutions per minute to prepare a novel carbon paste;

[0146] 3. 853 mg of stannous chloride and 338 mg of thiourea were added to 30 mL of deionized water, and the mixture was continuously stirred at room temperature for 36 hours. After centrifuging the product, the supernatant was retained to obtain a tin dioxide precursor solution. The tin dioxide precursor solution was preheated at 90 °C for 30 minutes, and the tin dioxide precursor solution was spin-coated on the surface-treated FTO glass substrate (2000 revolutions per minute, 30 seconds), and annealed at 200 °C for 1 hour to form a dense tin dioxide electron transport layer;

[0147] 4. 2.97 g of lead bromide powder was added to 8 mL of DMF (N-N dimethylformamide), and dissolved on a heating table at 90 °C to prepare a DMF solution of lead bromide with a concentration of 1 mol / L. 1.48 g of cesium bromide powder was added to a 100 mL volumetric flask, fixed volume with anhydrous methanol, and then sonicated to obtain a methanol solution of cesium bromide with a concentration of 0.07 mol / L;

[0148] 5. The DMF solution of lead bromide was preheated at 90 °C for 30 minutes, and 90 μL was taken and spin-coated on the film prepared in step 4 (2000 revolutions per minute, 30 seconds), and then annealed at 90 °C for 30 minutes to obtain a lead bromide film;

[0149] 6. The methanol solution of cesium bromide was spin-coated on the lead bromide film prepared in step 5 (2000 revolutions per minute, 30 seconds), heated and annealed at 250 °C for 5 minutes, cooled, and then spin-coated again. This operation was repeated 8 times to obtain a high-quality CsPbBr3 perovskite layer;

[0150] 7. Spin-coat the carbon paste obtained in Step 2 on the surface of the CsPbBr3 perovskite thin film obtained in Step 6, and heat and cure it at 50 °C for 1 hour to obtain the back electrode, and assemble a perovskite solar cell with the structure of FTO / tin dioxide electron transport layer / CsPbBr3 perovskite layer / carbon back electrode.

[0151] The photovoltaic performance parameters of the perovskite solar cells in the above examples and comparative examples are as follows:

[0152] Table 1 Photovoltaic performance parameters of the perovskite solar cells in the examples and comparative examples

[0153]

[0154] It can be seen from the comparison between the examples and the comparative examples that, compared with the pure carbon nanospheres derived from polymers, the transition metal chalcogenide in-situ composite N-doped carbon nanospheres as the back electrode can significantly improve the photovoltaic performance of the prepared perovskite solar cells, and the open-circuit voltage, short-circuit current density, and fill factor of the cells have been significantly improved. By comparing Examples 2, 4, 5 with the comparative examples, it can be obtained that: compared with the devices with pure carbon nanospheres as the back electrode, the devices using different transition metal chalcogenides such as MoS2, WS2, CuO2 in-situ composite doped N carbon nanospheres as the back electrode have significantly improved photovoltaic performance.

[0155] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a carbon back electrode, characterized in that, It includes the following steps: (1) Mix an ammonium transition metal chalcogenate, an emulsifier, water, and a monomer to obtain a mixed solution; (2) Mix an aqueous initiator solution and the mixed solution obtained in step (1), and then carry out a polymerization reaction. The resulting product is subjected to carbonization treatment to obtain heteroatom-rich carbon nanospheres composite with a transition metal chalcogenide; (3) Mix the heteroatom-rich carbon nanospheres composite with a transition metal chalcogenide obtained in step (2), other carbon materials, carbon black, a binder, and a solvent to obtain a carbon paste; The other carbon materials include one or more of carbon nanotubes, graphite, and carbon fibers; (4) Coat a preheated tin dioxide precursor solution on a substrate, and form a tin dioxide electron transport layer after annealing; (5) Coat a PbX2 solution on the tin dioxide electron transport layer, and form a PbX2 thin film after annealing; wherein, X includes I, Br, or Cl; (6) Coat an AY solution on the PbX2 thin film, and obtain a perovskite thin film after annealing; wherein, A includes a formamidine group, a methylamine group, or Cs, and Y includes I, Br, or Cl; (7) Deposit the carbon paste obtained in step (3) on the perovskite thin film obtained in step (6), and obtain a carbon back electrode after heating and curing; There is no limitation on the sequence between steps (1) to (3) as a whole and steps (4) to (6) as a whole.

2. The method according to claim 1, characterized in that, In step (1), the emulsifier includes one or more of TX-100, P135, and F127, and the dosage ratio of the emulsifier to water is 1-2 mg:1 mL; The monomer includes one or more of aniline, pyrrole, and thiophene, and the volume concentration of the monomer in the mixed solution is 1-2%; The ammonium transition metal chalcogenate includes one or more of ammonium tetrathiotungstate, ammonium tetrathiomolybdate, ammonium molybdate, ammonium paratungstate, ammonium copper sulfate, and ammonium nickel sulfate. The molar percentage of the ammonium transition metal chalcogenate in the monomer is 0-2%, and the dosage of the ammonium transition metal chalcogenate is not zero.

3. The method according to claim 1 or 2, characterized in that, In step (2), the initiator includes one or more of ammonium persulfate, potassium persulfate, and sodium persulfate, and the concentration of the aqueous initiator solution is 0.05-0.2 g / mL; The aqueous initiator solution and the mixed solution obtained in step (1) are refrigerated and then mixed. The refrigeration temperature is independently 0-5°C, and the refrigeration time is independently 30-60 min; The volume ratio of the aqueous initiator solution to the water in step (1) is 15-25:55-65; The temperature of the polymerization reaction is 0-5°C, and the time is 24-48 h; The temperature of the carbonization treatment is 700-1200°C, and the time is 3-6 h. The carbonization treatment is carried out under a protective atmosphere.

4. The method according to claim 3, characterized in that, In step (3), the mass ratio of the heteroatom-rich carbon nanospheres composite with a transition metal chalcogenide, other carbon materials, and carbon black is 5-7:2-3:1-2, and the mass ratio of the carbon materials, binder, and solvent is 2-3:0.5-1:7-8. The carbon materials refer to the sum of the heteroatom-rich carbon nanospheres composite with a transition metal chalcogenide, other carbon materials, and carbon black; The solvent includes one or more of terpineol, ethyl acetate, and chlorobenzene; The binder includes one or more of a cellulose-based binder, an acetate-based binder, a titanate-based binder, and an acrylate-based binder.

5. The method according to claim 1 or 2 or 4, characterized in that, In step (4), the temperature of the preheating is 50 - 90 °C, and the time is 0.5 - 1.5 h; The tin dioxide precursor solution is prepared from stannous chloride, thiourea, and water, and the dosage ratio of stannous chloride, thiourea, and water is 830 - 870 mg: 310 - 360 mg: 20 - 40 mL; The coating is spin coating, the speed of spin coating is 1500 - 2500 revolutions per minute, and the time of spin coating is 20 - 40 seconds; The annealing temperature is 150 - 250 °C, and the time is 0.5 - 2 h.

6. The method according to claim 5, characterized in that, In step (5), the concentration of the PbX2 solution is 0.8 - 1.8 mol / L, and the solvent includes N,N-dimethylformamide or dimethyl sulfoxide; The coating is spin coating, the speed of spin coating is 6000 - 8000 revolutions per minute, and the time of spin coating is 20 - 40 seconds; The annealing temperature is 70 - 100 °C, and the time is 0.5 - 2 h.

7. The method according to claim 1 or 2 or 4 or 6, characterized in that, In step (6), the concentration of the AY solution is 0.06 - 1.5 mol / L, and the solvent includes isopropyl alcohol or methanol; The coating is spin coating, the speed of spin coating is 6000 - 8000 revolutions per minute, and the time of spin coating is 20 - 40 seconds; The annealing temperature is 90 - 250 °C, and the time is 0.5 - 2 h.

8. The method according to claim 7, characterized in that, In step (7), the temperature of heat curing is 50 - 100 °C, and the time is 1 - 1.5 h; The thickness of the obtained carbon back electrode is 10 - 20 μm.

9. The carbon back electrode obtained by the method according to any one of claims 1 to 8.

10. A perovskite solar cell assembled from the carbon back electrode according to claim 9, characterized in that The perovskite solar cell is a perovskite solar cell based on a polymer-derived heteroatom-doped carbon in-situ composite transition metal chalcogenide back electrode; The open-circuit voltage of the perovskite solar cell is 1.45 - 1.65 V, and the short-circuit current density is 6.5 - 8.0 mA·cm -2 , the fill factor is 0.70 - 0.85, and the photoelectric conversion efficiency is 7.50 - 10.50%.

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