PEROVSKITE TANDEM SOLAR CELLS BASED ON A TUNNELING LAYER OF TWO-DIMENSIONAL LAYERED METAL CARBIDES AND METAL NITRIDES

Abstract

The invention relates to a perovskite tandem solar cell based on a tunneling layer of two-dimensional layered metal carbides and metal nitrides, the tunneling junction composite layer is prepared by using two-dimensional layered metal carbides and metal nitrides, a dense layer is arranged on one side of the tunneling junction composite layer, and a transport layer is arranged on the other side. The two-dimensional layered metal carbide and metal nitride materials are selected from graphene, Ti3C2Tx, Mo2CTx, V2CTx, Nb2CTx and Ti2CTx. The tunneling junction structure of the invention can effectively reduce the light loss in the tandem solar cell and the interface recombination of the tandem cell, which can significantly improve the photocurrent generation and charge transfer of the perovskite/perovskite tandem solar cell, and improve the power conversion efficiency of the perovskite/perovskite tandem solar cell.

Claims

1. Perovskite tandem solar cells based on a tunneling layer of two-dimensional layered metal carbides and metal nitrides: a tunneling junction composite layer is prepared by using two-dimensional layered metal carbides and metal nitrides, a dense layer is arranged on one side of the tunneling junction composite layer, and a transport layer is arranged on the other side; the two-dimensional layered metal carbide and metal nitride materials are selected from graphene, Ti3C2Tx, Mo2CTx, V2CTx, Nb2CTx, Ti2CTx.

2. The perovskite tandem solar cells according to claim 1, the dense layer is prepared by n-type semiconductor materials, and the transport layer is prepared by p-type semiconductor materials; or, the dense layer is prepared by p-type semiconductor materials, and the transport layer is prepared by n-type semiconductor materials.

3. The perovskite tandem solar cells according to claim 1, perovskite tandem solar cells based on a tunneling layer of two-dimensional layered metal carbides and metal nitrides, the structure of the perovskite/perovskite tandem solar cell described in this paper is p-i-n type, which includes conductive substrate, p-type hole transport layer, wide band gap perovskite film, n-type electron transport layer, n-type dense layer, tunneling junction composite layer, p-type hole transport layer, narrow band gap perovskite film, n-type electron transport layer and metal back electrode from bottom to top; or, the structure of the perovskite/perovskite tandem solar cell is n-i-p type, which includes transparent conductive substrate, n-type electron transport layer, wide band gap perovskite film, p-type hole transport layer, p-type dense layer, tunneling junction composite layer, n-type electron transport layer, narrow band gap perovskite film, p-type hole transport layer and metal back electrode from bottom to top.

4. The perovskite tandem solar cells according to claim 1, the preparation of Ti.sub.3C.sub.2T.sub.x two-dimensional layered structure material includes the following steps: Step 1: firstly, under the protection of nitrogen in the glove box, weighing the raw materials according to the ratio of TiC:Ti:Si:NaCl:KCl=2:1:1.1:4:4, then, thoroughly mixing the weighed raw materials, and taking out the obtained mixed powder from the glove box and putting it into the planetary ball mill to fully mash for 5 h, and putting the mashed powder into the alumina crucible; then putting the alumina crucible into a tube furnace, and conducting heat treatment at a rate of 4? C./min to 1100? C. for 3 h under the protection of argon atmosphere, after the reaction, cooing the tube furnace to room temperature at a rate of 4? C./min, and then removing NaCl and KCl by washing with deionized water, drying the residual product at 60? C. to obtain the Si-MAX phase precursor; Step 2: under the protection of nitrogen in the glove box, thoroughly mixing the raw materials according to the molar ratio of Si-MAX phase precursor:ZnCl2=1:6, and then taking out the obtained mixed powder from the glove box and placing it in a planetary ball mill for 3 h, and then placing the powder in an alumina crucible; putting the alumina crucible into a tube furnace and conducting heat treatment at 550? C. for 5 h under argon protection; after the reaction, removing the residual ZnCl2 by washing with deionized water, and obtaining the reaction product Ti3SiC2 MAX phase by drying at 40? C.; Step 3: immersing the prepared Ti3SiC2 MAX phase in molten CuCl2 Lewis molten salt at 750? C. for 6 h, the Si atoms weakly bound to Ti in the Ti.sub.3C.sub.2 sublayer, which are oxidized to Si4+ cation by Lewis acid Cu2+, so as to form a volatile SiCl4 phase, at the same time, Cu2+ is reduced to Cu metal, Ti3SiC2 reacts with CuCl2 to form Ti3C2Cl2; further immersing Ti3C2Cl2 powder and Cu metal in ammonium persulfate solution to remove Cu particles on the surface and increase O-surface groups, after the reaction, centrifugalizing, washing and drying the suspension to obtain Ti3C2Tx MXene.

5. The perovskite tandem solar cells according to claim 1, Mo2CTx two-dimensional layered structure material is prepared by the following method: slowly adding 2 g of Mo2Ga2C powder into 20 mL HF solution, stirring the mixed solution containing Mo2Ga2C in a magnetic stirring heating sleeve at 55? C. for 7 h, and then centrifugalizing it at 10000 rpm for 10 min, harvesting the product and then washing it several times with deionized water until the pH of the solution is 6, drying the obtained powder in a freeze dryer to finally obtain Mo2CTx.

6. The perovskite tandem solar cells according to claim 1, the preparation of V2CTX two-dimensional layered structure material includes the following steps: (1) in the resistance furnace, continuously introducing hydrogen, heating V2O5 to 600? C. for 3 h, then heating to 1000? C. for 5 h, and finally cooling with the furnace to obtain V2O3; (2) after mixing V2O3, Al.sub.2O.sub.3 and nano-carbon powder with PVB binder, mixing it with agate mortar for half an hour, then, pressing 0.5 g of metal oxide/carbon powder mixture by a pressure prototype under 10 MPa pressure to form a cylindrical block with a diameter of 10 mm, which is used as the cathode material; (3) carrying out the molten salt electrolysis process in a vertical resistance furnace; the electrolytic cell is composed of a metal oxide/carbon cathode, a graphite anode, an external power supply, and an alumina crucible containing an electrolyte; continuously introducing high-purity argon into the electrolytic cell, and performing electrolysis between the cathode and the graphite anode at 2.8V for at least 12 h to remove moisture and other impurities in calcium chloride; the electrolytic cell composed of metal oxide/carbon cathode and graphite anode is electrolyzed at 850? C. and 3.1V electrolysis voltage, applying direct current through a constant voltage power supply, washing the obtained cathode product with deionized water to remove the residual calcium chloride molten salt, and drying it in a vacuum oven to obtain the MAX phase powder V2AlC; (4) immersing the V2AlC powder obtained after electrolysis in hydrofluoric acid solution to etch the aluminum atom layer, and immersing the etched V2CTX MXene material in 1 mol/L KOH solution, then stirring it with a magnetic stirrer for 24 h, collecting the precipitate by centrifugation and washing it to obtain two-dimensional V2CTX MXene material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 is a schematic diagram of the device structure of the perovskite/perovskite tandem solar cell in the invention. FIG. 1 (left) is a p-i-n structure perovskite/perovskite tandem solar cell device, and FIG. 1 (right) is an n-i-p perovskite tandem solar cell device.

[0037] FIG. 2 is a schematic diagram of the synthesis process of MAX phase powder V.sub.2AlC.

[0038] FIG. 3 is the volt-ampere characteristic curve of the p-i-n structure perovskite/perovskite tandem solar cell device in Embodiment 1.

[0039] FIG. 4 is the volt-ampere characteristic curve of the n-i-p structure perovskite/perovskite tandem solar cell device in Embodiment 2.

[0040] FIG. 5 shows the element content of Ti.sub.3CCl.

[0041] FIG. 6 is the SEM diagram of Ti.sub.3CCl.

[0042] FIG. 7 is the XRD pattern of Ti.sub.3C.sub.2Cl.sub.2 MXene prepared by molten salt method.

[0043] FIG. 8 is the XRD comparison diagram of Ti.sub.3ZnC.sub.2 and Ti.sub.3Al.sub.2C.sub.2.

[0044] FIG. 9 and FIG. 10 are the SEM diagrams of Ti.sub.3C.sub.2T.sub.x MXene prepared by molten salt method.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following will be combined with the drawings of the embodiments of the invention to clearly and completely describe the technical scheme of the embodiments of the invention. The described embodiments are only part of the embodiments of the invention, not all of the embodiments.

[0046] As shown in FIG. 1, the invention designs a tunneling junction structure of perovskite/perovskite tandem solar cell, which is composed of a dense layer, a two-dimensional layered film tunneling junction composite layer and a transport layer. In this structure, the dense layer is prepared by n-type or p-type semiconductor materials, and the transport layer is prepared by the corresponding p-type or n-type semiconductor materials. Among them, n-type semiconductor materials have the ability to transport electrons and block hole transport, and p-type semiconductor materials have the ability to transport holes and block electron transmission.

[0047] In the tunneling junction structure of the invention, the n-type or p-type dense layer plays a role in protecting the wide band gap perovskite solar cell (top solar cell) from being destroyed by the subsequent narrow band gap perovskite solar cell (bottom solar cell) in the subsequent preparation process by organic solvent or vacuum sputtering, and the dense layer has the ability to transmit electrons or holes; the two-dimensional layered thin film layer is a tunneling junction composite layer in tandem solar cell. Because of its excellent conductivity, it can play the role of tunneling recombination of electrons or holes and reduce interface charge recombination. At the same time, its excellent light transmittance can allow the incident light to pass through the tunneling junction layer and enter the narrow band gap solar cell, reduce the light loss at the tunneling junction and increase the photocurrent density, thereby improving the power conversion efficiency of the perovskite/perovskite tandem solar cell.

[0048] In this invention, a two-dimensional layered thin film layer can be two-dimensional layered structure of metal carbide and metal nitride materials (such as graphene, Ti.sub.3C.sub.2T.sub.x, Mo.sub.2CT.sub.x, V.sub.2CT.sub.x, Nb.sub.2CT.sub.x, Ti.sub.2CT.sub.x, etc.), but not limited to the two-dimensional layered structure materials listed above. The two-dimensional layered film layer can be a continuous two-dimensional layered film, or a two-dimensional layered structure of metal carbide and metal nitride material particle film or a non-dense two-dimensional layered structure of metal carbide and metal nitride material island nanosheet layer. Two-dimensional layered thin film can be prepared by spin coating, scraping, spraying, pulsed laser deposition, magnetron sputtering, chemical vapor deposition and other deposition methods.

[0049] The dense layer can be prepared by physical deposition or chemical deposition. Physical deposition methods include but are not limited to vacuum evaporation, sputtering, ion beam deposition, pulsed laser deposition, etc.; chemical deposition methods include but are not limited to chemical vapor deposition, atomic layer deposition, sol-gel, spin coating, etc.

[0050] The tunneling junction structure of the invention is applied to the perovskite/perovskite tandem solar photovoltaic cell, and two kinds of perovskite tandem solar cells with different structures of p-i-n and n-i-p can be designed. As shown in FIG. 1 (left), the perovskite tandem solar cell is a p-i-n structure, which includes transparent conductive substrate, p-type hole transport layer, wide band gap perovskite film, n-type electron transport layer, n-type dense layer, tunneling junction composite layer, p-type hole transport layer, narrow band gap perovskite film, n-type electron transport layer and back electrode from bottom to top. As shown in FIG. 1 (right), the n-i-p structure of perovskite tandem solar cells includes transparent conductive substrate, n-type electron transport layer, wide band gap perovskite film, p-type hole transport layer, p-type dense layer, tunneling composite layer, n-type electron transport layer, narrow band gap perovskite film, p-type hole transport layer and back electrode from bottom to top.

[0051] Specifically, in the p-i-n structure:

[0052] the transparent conductive substrates are indium tin oxide (ITO) and fluorine-doped indium tin oxide (FTO), but not limited to the above listed.

[0053] The n-type dense layer or transport layer can be made of one or more n-type semiconductor materials such as titanium oxide (TiO.sub.2), tin oxide (SnO.sub.2), zinc oxide (ZnO), vanadium oxide (V.sub.2O.sub.5), zinc oxide tin (Zn.sub.2SnO.sub.4), but not limited to the n-type semiconductor materials listed above.

[0054] The p-type hole transport layer can be prepared by one or more p-type semiconductor materials such as Nickel oxide (NiO), molybdenum oxide (MoO.sub.3), cuprous oxide (Cu.sub.2O), copper iodide (CuI), copper phthalocyanine (CuPc), cuprous thiocyanate (CuSCN), redox graphene, poly [bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA),2,2,7,7-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene (Spiro-OMeTAD), poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS), 4-butyl-N, N-diphenylaniline homopolymer (PloyTPD), and polyvinyl carbazole (PVK), but not limited to the p-type semiconductor materials listed above.

[0055] Specifically, in the n-i-p structure:

[0056] The p-type dense layer or hole transport layer can be prepared by one or more p-type semiconductor materials such as nickel oxide (NiO), molybdenum oxide (MoO.sub.3), cuprous oxide (Cu.sub.2O), copper iodide (CuI), copper phthalocyanine (CuPc), cuprous thiocyanate (CuSCN), but not limited to the p-type semiconductor materials listed above.

[0057] The n-type hole transport layer can be made of one or more n-type semiconductor materials such as titanium oxide (TiO.sub.2), tin oxide (SnO.sub.2), zinc oxide (ZnO), fullerene (C.sub.60), graphene, fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), but not limited to the n-type semiconductor materials listed above.

[0058] The following is a further explanation of the above scheme in combination with specific embodiments.

Embodiment 1

[0059] This Embodiment. 1 uses the structure shown in FIG. 1 (left) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0060] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15?20 min, and it is also put into the oven at 75? C., and then the cleaned conductive glass substrate is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0061] 2. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a p-type transport layer. 631 mg of PTAA is dissolved in 2 mL of chlorobenzene, the PTAA solution is dropped on the glass substrate and rotated at 2000 rpm for 20s, then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of about 20 nm.

[0062] 3. A layer of wide band gap perovskite film is deposited on the basis of the previous step, CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are prepared by dissolving 124 mg PbCl.sub.2 and 23 mg CH.sub.3NH.sub.3I, 92 mg PbBr.sub.2 and 23 mg CH.sub.3NH.sub.3Br in 2 mL DMF solution respectively. Then CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are mixed at a ratio of 3:2 to obtain CH.sub.3NH.sub.3Pb (I.sub.0.6Br.sub.0.4).sub.3 solution, and then 50 ?L solution is rotated at 4000 rpm for 60s, and annealed at 100? C. for 1 min, then annealed at 150? C. for 10 min to obtain a layer of wide band gap perovskite film with a thickness of about 300 nm.

[0063] 4. A layer of fullerene (C.sub.60) is prepared by thermal evaporation as an n-type transport layer, the prepared substrate is transferred to the thermal evaporation chamber, and the C.sub.60 thin film layer is prepared by high vacuum evaporation coating machine. Firstly, the vacuum degree of the evaporation space is pumped below 10 Pa by a mechanical pump, and a secondary molecular pump is enabled to achieve a high vacuum environment, when the vacuum degree of the evaporation space reaches below 5?10.sup.?3 Pa, the final preparation of 20 nm C.sub.60 film is completed at an evaporation rate of 0.2 ?/s.

[0064] 5. A layer of SnO.sub.2 is grown on the basis of the previous step by atomic layer deposition (ALD) as an n-type dense layer with a thickness of 20 nm.

[0065] 6. The tunneling junction composite layer is prepared by spin coating method, the Ti.sub.3C.sub.2T.sub.x powder prepared in the early stage is mixed with isopropanol at a mass ratio of 2:7, then the solution is shaken on a vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 15 min, then 70 ?L solution is taken to drop the composite layer solution on the glass substrate, and the rotation speed is set at 3500 rpm, the time is 30s. The spin-coated glass is annealed on heating stage at 60? C. for 15 min to obtain a tunneling junction composite layer.

[0066] 7. A layer of PTAA is prepared by spin coating technology as a p-type transport layer, P3HT solution configuration: 15 mg of P3HT solid powder is dissolved in 1 mL of CB solvent (solution concentration of 15 mg/mL), heated and stirred overnight at 50? C., and then 70 ?L of solution is spin-coated at 2000 rpm for 60s without annealing, then the thickness of the obtained P3HT layer is 100 nm.

[0067] 8. On the basis of the previous step, a layer of narrow band gap perovskite film is deposited, and the precursor solution of FA.sub.0.7MA.sub.0.3Pb.sub.0.5Sn.sub.0.5I.sub.3 is prepared, 2M precursor solution is prepared in a mixed solution with a volume ratio of DMF:DMF of 1.5 mL:0.5 mL, the mass of FAI and MAI is 0.2408 g and 0.0954 g respectively; the mass of PbI.sub.2/SnI.sub.2 is 0.4620 g/0.374 g respectively. 0.0374 g of SnF.sub.2 is added to the precursor solution, and the precursor solution is stirred at room temperature for 2 h, the precursor solution is filtered by using 0.20 ?m PTFE membrane. In order to reduce the Sn.sup.4+ in the precursor solution, 10 mg of tin powder is added to the precursor and it is stirred at room temperature for 10 min. FA.sub.0.7MA.sub.0.3Pb.sub.0.5Sn.sub.0.5I.sub.3perovskite solution is prepared by filtering the precursor solution containing residual tin powder through a 0.20 ?m PTFE filter membrane. During the spin coating, a two-step rotation process is used: (1) 1000 rpm/min for 10s, acceleration of 200 rpm/min; (2) 4000 rpm/min for 40s, acceleration of 1000 rpm/min. In the second step of spin coating, ethyl acetate is dripped 20 seconds before the end of the procedure, ethyl acetate is selected because it is less toxic and more environmentally friendly than the commonly used chlorobenzene. The substrate is then transferred to a heating plate and heated at 100? C. for 10 min.

[0068] 9. A layer of fullerene (C.sub.60) and BCP is prepared by thermal evaporation as an n-type transport layer, the final preparation of 20 nm C.sub.60 film is completed at an evaporation rate of 0.2 ?/s, and the final preparation of 7 nm BCP film is completed at an evaporation rate of 0.2 ?/s.

[0069] 10. The metal electrode is deposited by thermal evaporation, and a layer of Cu with a thickness of 120 nm is evaporated at 0.5 ?/s as the metal electrode.

[0070] As shown in FIG. 3, the use of two-dimensional layered metal carbides and metal nitrides as the tunneling layer material can not only reduce the loss of incident light, but also provide conductivity and increase the short-circuit current density of the tandem solar cell. In addition, this one-step deposition of two-dimensional layered metal carbide and metal nitride materials has good compactness, which can reduce the voltage loss and improve the open circuit voltage of the tandem solar cell. In the absence of two-dimensional layered film tunneling junction composite layer, the power conversion efficiency of the device is only 18.04%; after preparing a two-dimensional layered film as a tunneling composite layer, the power conversion efficiency can be increased to 24.41%.

Embodiment 2

[0071] This Embodiment 2 uses the structure shown in FIG. 1 (right) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0072] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15?20 min, and it is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0073] 2. A layer of SnO.sub.2 is prepared by chemical bath deposition (CBD) as an n-type transport layer. Firstly, SnCl.sub.2-2H.sub.2O mother liquor needs to be prepared. 5 g urea is dissolved in 400 mL deionized water, and then 100 ?L mercaptoacetic acid and 5 mL HCl (37 wt %) are added, finally, 1.096 g SnCl.sub.2-2H.sub.2O powder is dissolved into 0.012M solution, the solution is fully oscillated, mixed and placed in the refrigerator for three days. Then, the SnO.sub.2 layer is deposited, the cleaned ITO conductive glass is put into the UV cleaning machine for 15 min to remove the organic stains on the surface of the glass and improve the surface wettability. 200 ?L of standing SnCl.sub.2.Math.2H.sub.2O mother liquor is mixed with 100 mL of deionized water to prepare a 0.02M diluent, and then the treated ITO substrate is immersed in the prepared diluent and placed in an oven at 60? C. for 1 h. After fully reacting, the solution is repeatedly rinsed with deionized water until it is clear and transparent, and then dried by air gun, the CBD steps are repeated twice to ensure the formation of a dense and appropriate thickness of SnO.sub.2 layer. Finally, n-type transport is obtained by annealing at 150? C. on a heating stage for 1 h.

[0074] 3. A layer of wide band gap perovskite film is deposited on the basis of the previous step. CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are prepared by dissolving 124 mg PbCl.sub.2 and 23 mg CH.sub.3NH.sub.3I, 92 mg PbBr.sub.2 and 23 mg CH.sub.3NH.sub.3Br in 2 mL DMF solution respectively. Then CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are mixed at a ratio of 3:2 to obtain CH.sub.3NH.sub.3Pb (I.sub.0.6Br.sub.0.4).sub.3 solution, and then 50 ?L solution is rotated at 4000 rpm for 60s, and annealed at 100? C. for 1 min, then annealed at 150? C. for 10 min to obtain a layer of wide band gap perovskite film with a thickness of about 300 nm.

[0075] 4. A layer of P3HT is prepared by spin coating technology as a p-type transport layer. P3HT solution configuration: 15 mg of P3HT solid powder is dissolved in 1 mL of CB solvent (solution concentration of 15 mg/mL), heated and stirred overnight at 50? C., and then spin-coated at 2000 rpm for 60s without annealing, the thickness of the obtained P3HT layer is 100 nm.

[0076] 5. A layer of NiO.sub.x is grown on the basis of the previous step by atomic layer deposition (ALD) as an p-type dense layer with a thickness of 10 nm.

[0077] 6. The tunneling junction composite layer is prepared by spin coating method, the Ti.sub.3C.sub.2 T.sub.x powder prepared in the early stage is mixed with isopropanol at a mass ratio of 2:7, then the solution is shaken on a vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 15 min to break the large molecular particles, then 70 ?L solution is taken to drop the composite layer solution on the glass substrate, and the rotation speed is set at 3500 rpm, the time is 30s. The spin-coated glass is annealed on a heating stage at 60? C. for 15 min to obtain a tunneling junction composite layer.

[0078] 7. The preparation of C.sub.60-n type transport layer is prepared by thermal evaporation technology, the prepared substrate is transferred to the thermal evaporation chamber, and the C.sub.60 thin film layer is prepared by high vacuum evaporation coating machine. Firstly, the vacuum degree of the evaporation space is pumped below 10 Pa by a mechanical pump, and a secondary molecular pump is enabled to achieve a high vacuum environment, when the vacuum degree of the evaporation space reaches below 5?10.sup.?3 Pa, the deposition of 20 nm thin film is completed at an evaporation rate of 0.2 ?/s.

[0079] 8. On the basis of the prepared C.sub.60 layer, a layer of narrow band gap perovskite film is prepared, and the precursor solution of FA.sub.0.7MA.sub.0.3Pb.sub.0.5Sn.sub.0.5I.sub.3 is also prepared, 2M precursor solution is prepared in a mixed solution with a volume ratio of DMF:DMF of 1.5 mL:0.5 mL, the mass of FAI and MAI is 0.2408 g and 0.0954 g respectively; the mass of PbI.sub.2/SnI.sub.2 is 0.4620 g/0.374 g respectively. 0.0374 g SnF.sub.2 is added to the precursor solution, and the precursor solution is stirred at room temperature for 2 h, the precursor solution is filtered by using 0.20 ?m PTFE membrane. In order to reduce the Sn.sup.4+ in the precursor solution, 10 mg of tin powder is added to the precursor and then it is stirred at room temperature for 10 min for using. FA.sub.0.7MA.sub.0.3Pb.sub.0.5Sn.sub.0.5I.sub.3perovskite solution is prepared by filtering the precursor solution containing residual tin powder through a 0.20 ?m PTFE filter membrane. During the spin coating, a two-step rotation process is used: (1) 1000 rpm/min for 10s, acceleration of 200 rpm/min; (2) 4000 rpm/min for 40s, acceleration of 1000 rpm/min. In the second step of spin coating, ethyl acetate is dripped 20 seconds before the end of the procedure, ethyl acetate is selected because it is less toxic and more environmentally friendly than the commonly used chlorobenzene. The substrate is then transferred to a heating stage and heated at 100? C. for 10 min.

[0080] 9. A layer of Spiro-OMeTAD is prepared by spin coating technology as a p-type transport layer. 520 mg of lithium bis (trifluoromethanesulfonyl) imide powder is added to 1 mL of acetonitrile (ACN), and the lithium salt solution is obtained by stirring at room temperature for 3 h in a magnetic stirrer until it is dissolved. 450 mg FK209 powder is added to 1 mL acetonitrile (ACN) and stirred at room temperature for 3 h in a magnetic stirrer to dissolve to obtain FK209 solution. A total of 71 mg Spiro-OMeTAD, 31 ?L lithium salt, 25.6 ?L TBP solution, 18.5 ?L FK209 solution and 1 mL chlorobenzene are added to a 3 mL glass bottle to prepare Spiro-OMeTAD hole transport layer solution, the spin coating instrument program is set to 5000 rpm for 30s, the 40 ?L Spiro-OMeTAD solution is weighed by a pipette, and the P-type transport layer is prepared by dynamic spin coating solution on the perovskite film.

[0081] 10. Finally, by using the thermal evaporation source, a layer of Au with a thickness of 100 nm is evaporated at a speed of 0.5 ?/s as a back electrode.

[0082] As shown in FIG. 4, using the solar cells prepared in the structure of Embodiment 2 can not only reduce the loss of incident light, but also provide conductivity and increase or decrease the short-circuit current density of the tandem solar cell. In addition, this one-step deposition of two-dimensional layered metal carbide and metal nitride materials has good compactness, which can reduce the voltage loss and improve the open circuit voltage of the tandem solar cell. In the absence of the two-dimensional layered film tunneling junction composite layer, the power conversion efficiency of the device is only 19.66%; after the two-dimensional layered film prepared in Embodiment 2 is used as the tunneling composite layer, the power conversion efficiency is increased to 24.33%.

Embodiment 3

[0083] This Embodiment 3 uses the structure shown in FIG. 1 (left) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0084] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15?20 min, and it is also put into the oven at 75? C., and then the cleaned conductive glass substrate is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0085] 2. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a p-type transport layer. 631 mg of PTAA is dissolved in 2 mL of chlorobenzene, the PTAA solution is dropped on the glass substrate and rotated at 2000 rpm for 20s, then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of about 20 nm.

[0086] 3. A layer of wide band gap perovskite film is deposited on the basis of the previous step, CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are prepared by dissolving 124 mg PbCl.sub.2 and 23 mg CH.sub.3NH.sub.3I, 92 mg PbBr.sub.2 and 23 mg CH.sub.3NH.sub.3Br in 2 mL DMF solution respectively. Then CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are mixed at a ratio of 3:2 to obtain CH.sub.3NH.sub.3Pb (I.sub.0.6Br.sub.0.4).sub.3 solution, and then 50 ?L solution is rotated at 4000 rpm for 60s, and annealed at 100? C. for 1 min, then annealed at 150? C. for 10 min to obtain a layer of wide band gap perovskite film with a thickness of about 300 nm.

[0087] 4. A layer of fullerene (C.sub.60) is prepared by thermal evaporation as an n-type transport layer, the prepared substrate is transferred to the thermal evaporation chamber, and the C.sub.60 thin film layer is prepared by high vacuum evaporation coating machine. Firstly, the vacuum degree of the evaporation space is pumped below 10 Pa by a mechanical pump, and a secondary molecular pump is enabled to achieve a high vacuum environment, when the vacuum degree of the evaporation space reaches below 5?10.sup.?3 Pa, the deposition of 20 nm thin film is completed at an evaporation rate of 0.2 ?/s.

[0088] 5. A layer of SnO.sub.2 is grown on the basis of the previous step by atomic layer deposition (ALD) as an n-type dense layer with a thickness of 20 nm.

[0089] 6. The tunneling junction composite layer is prepared by spin coating method, the Mo.sub.2CT.sub.x powder prepared in the early stage is mixed with isopropanol at a mass ratio of 2:10, then the solution is shaken on a vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 20 min, then 50?70 ?L solution is taken to drop the composite layer solution on the glass substrate, and the rotation speed is set at 5000 rpm for 25s, the spin-coated glass is annealed on a heating stage at 80? C. for 15 min to obtain a tunneling junction composite layer.

[0090] 7. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a p-type transport layer. 631 mg of PTAA is dissolved in 2 mL of chlorobenzene, the PTAA solution is dropped on the glass substrate and rotated at 2000 rpm for 20s, then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of about 20 nm.

[0091] 8. On the basis of the previous step, a layer of narrow band gap perovskite film is prepared, and the precursor solution of CsPb.sub.0.4Sn.sub.0.6I.sub.2Br is also prepared: in a nitrogen-filled glove box, CsI:(PbI.sub.2+PbBr.sub.2):(SnI.sub.2+SnBr.sub.2): SnF.sub.2 is weighed at a stoichiometric molar ratio of 1:0.4:0.6:0.1 and dissolved in an organic mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide (DMF:DMSO=3:7) to prepare a 1 mol/L precursor solution, after stirring at room temperature for 10-12 h, it is filtered by a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.22 ?m, and then 50 ?L of perovskite precursor solution is taken by a pipette, the perovskite precursor is dropped on the substrate, adjusted to 4000 rpm, and spin-coated for 30s. The spin-coated substrate is annealed on a heating at 120? C. stage for 10 min. A narrow band gap perovskite film with a thickness of about 300 nm is prepared.

[0092] 9. A layer of C.sub.60 and BCP is grown by thermal evaporation technology at 0.2 ?/s evaporation rate as an n-type transport layer, the thickness of C.sub.60 is 20 nm and the thickness of BCP is 7 nm.

[0093] 10. Finally, by using the thermal evaporation source, a layer of Au with a thickness of 100 nm is evaporated at a speed of 0.5 ?/s as a metal electrode.

Embodiment 4

[0094] This Embodiment 4 uses the structure shown in FIG. 1 (right) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0095] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15?20 min, and it is also put into the oven at 75? C., and then the cleaned conductive glass substrate is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0096] 2. A layer of SnO.sub.2 is prepared by chemical bath deposition (CBD) as an n-type transport layer. Firstly, SnCl.sub.2-2H.sub.2O mother liquor needs to be prepared. 5 g urea is dissolved in 400 mL deionized water, and then 100 ?L mercaptoacetic acid and 5 mL HCl (37 wt %) are added, finally, 1.096 g SnCl.sub.2-2H.sub.2O powder is dissolved into 0.012M solution, the solution is fully oscillated, mixed and placed in the refrigerator for three days. Then, the SnO.sub.2 layer is deposited. The cleaned ITO conductive glass is put into the UV cleaning machine for 15 min to remove the organic stains on the surface of the glass and improve the surface wettability. 200 ?L of standing SnCl.sub.2 2H.sub.2O mother liquor is mixed with 100 mL of deionized water to prepare a 0.02M diluent, and then the treated ITO substrate is immersed in the prepared diluent and placed in an oven at 60? C. for 1 h. After fully reacting, the solution is repeatedly rinsed with deionized water until it is clear and transparent, and then dried by air gun, the CBD steps are repeated twice to ensure the formation of a dense and appropriate thickness of SnO.sub.2 layer. Finally, n-type transport is obtained by annealing at 150? C. on a heating stage for 1 h.

[0097] 3. A layer of wide band gap perovskite film is deposited on the basis of the previous step. CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are prepared by dissolving 124 mg PbCl.sub.2 and 23 mg CH.sub.3NH.sub.3I, 92 mg PbBr.sub.2 and 23 mg CH.sub.3NH.sub.3Br in 2 mL DMF solution respectively. Then CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are mixed at a ratio of 3:2 to obtain CH.sub.3NH.sub.3Pb (I.sub.0.6Br.sub.0.4).sub.3 solution, and then 50 ?L solution is rotated at 4000 rpm for 60s, and annealed at 100? C. for 1 min, then annealed at 150? C. for 10 min to obtain a layer of wide band gap perovskite film with a thickness of about 300 nm.

[0098] 4. Poly [bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a p-type transport layer. 631 mg of PTAA is dissolved in 2 ml of chlorobenzene, the PTAA solution is dropped on the glass substrate and rotated at 2000 rpm for 20s, then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of about 20 nm.

[0099] 5. A layer of NiO.sub.x is grown on the substrate by atomic layer deposition (ALD) as a p-type dense layer with a thickness of 10 nm.

[0100] 6. The tunneling junction composite layer is prepared by spin coating method, the Mo.sub.2CT.sub.x powder prepared in the early stage is mixed with isopropanol at a mass ratio of 2:10, then the solution is shaken on a vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 20 min to break the large molecular particles, then 50?70 ?L solution is taken to drop the composite layer solution on the glass substrate, and the rotation speed is set at 5000 rpm for 25s. The spin-coated glass is annealed on a heating stage at 60? C. for 15 min to obtain a tunneling junction composite layer.

[0101] 7. The preparation of C.sub.60-n type transport layer is prepared by thermal evaporation technology, the prepared substrate is transferred to the thermal evaporation chamber, and the C.sub.60 thin film layer is prepared by high vacuum evaporation coating machine. Firstly, the vacuum degree of the evaporation space is pumped below 10 Pa by a mechanical pump, and a secondary molecular pump is enabled to achieve a high vacuum environment, when the vacuum degree of the evaporation space reaches below 5?10.sup.?3 Pa, the deposition of 20 nm thin film is completed at an evaporation rate of 0.2 ?/s.

[0102] 8. On the basis of the prepared Coo layer, a layer of narrow band gap perovskite film is prepared, and the precursor solution of CsPb.sub.0.4Sn.sub.0.6I.sub.2Br is also prepared: in a nitrogen-filled glove box, CsI:(PbI.sub.2+PbBr.sub.2):(SnI.sub.2+SnBr.sub.2): SnF.sub.2 is weighed at a stoichiometric molar ratio of 1:0.4:0.6:0.1 and dissolved in an organic mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide (DMF:DMSO=3:7) to prepare a 1 mol/L precursor solution, after stirring at room temperature for 10-12 h, it is filtered by a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.22 ?m, and then 50 ?L of perovskite precursor solution is taken with a pipette, the perovskite precursor is dropped on the substrate, adjusted to 4000 rpm, and spin-coated for 30s. The spin-coated substrate is annealed at 120? C. on a heating stage for 10 min. A narrow band gap perovskite film with a thickness of about 300 nm is prepared.

[0103] 9. A layer of Spiro-OMeTAD is prepared by spin coating technology as a p-type transport layer. 520 mg of lithium bis (trifluoromethanesulfonyl) imide powder is added to 1 mL of acetonitrile (ACN), and the lithium salt solution is obtained by stirring at room temperature for 3 h in a magnetic stirrer until it is dissolved. 450 mg FK209 powder is added to 1 mL acetonitrile (ACN) and stirred at room temperature for 3 h in a magnetic stirrer to dissolve to obtain FK209 solution. A total of 71 mg Spiro-OMeTAD, 31 ?L lithium salt, 25.6 ?L TBP solution, 18.5 ?L FK209 solution and 1 mL chlorobenzene are added to a 3 mL glass bottle to prepare Spiro-OMeTAD hole transport layer solution, the spin coating instrument program is set to 5000 rpm for 30s, the 40 ?L Spiro-OMeTAD solution is weighed by a pipette, and the P-type transport layer with a thickness of about 100 nm is prepared by dynamic spin-coating the solution on the perovskite film.

[0104] 10. Finally, by using the thermal evaporation source, a layer of Cu with a thickness of 100 nm is evaporated at a speed of 0.5 ?/s as a back electrode.

Embodiment 5

[0105] This Embodiment 5 uses the structure shown in FIG. 1 (left) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0106] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15?20 min, and it is also put into the oven at 75? C., and then the cleaned conductive glass substrate is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0107] 2. NiO.sub.x: 0.5 mol nickel nitrate hexahydrate is dissolved in 100 mL deionized water to obtain a dark green solution. NaOH solution (10 mol/L) is dropped into nickel nitrate hexahydrate solution until the pH value of the solution is 10. The colloidal precipitate is obtained by stirring at 40? C. for 10 min. The precipitate is washed twice with deionized water, dried at 80? C. for 6 h to obtain green powder, and calcined at 270? C. for 2 h to obtain dark black powder NiO.sub.x. NiO.sub.x and isopropanol are configured in a ratio of 3 mg:1 ml, and 80 ?L of NiO.sub.x aqueous solution is spin-coated on a cleaned ITO substrate at a speed of 3000 rpm/min for 30s. Then the sample is annealed at 110? C. for 20 min to obtain nickel oxide p-type transport layer.

[0108] 3. A layer of wide band gap perovskite film is deposited on the basis of the previous step, CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are prepared by dissolving 124 mg PbCl.sub.2 and 23 mg CH.sub.3NH.sub.3I, 92 mg PbBr.sub.2 and 23 mg CH.sub.3NH.sub.3Br in 2 mL DMF solution respectively. Then CH.sub.3 NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are mixed at a ratio of 3:2 to obtain CH.sub.3NH.sub.3Pb (I.sub.0.6Br.sub.0.4).sub.3 solution, and then 50 ?L solution is rotated at 4000 rpm for 60s, and annealed at 100? C. for 1 min, then annealed at 150? C. for 10 min to obtain a layer of wide band gap perovskite film with a thickness of about 300 nm.

[0109] 4. ZnO nanoparticles: 1.96 g of zinc acetate dihydrate (C.sub.4H.sub.10O.sub.6Zn) is dissolved in 60 mL of anhydrous ethanol and stirred for 30 min, the obtained solution is transferred to a 100 mL hydrothermal kettle and heated at 150? C. for 12 h. After heating, the solution is cooled to room temperature, the supernatant is removed, the precipitate is washed twice with ethanol water, dried overnight at 60? C., and then calcined at 480? C. for 3 h to obtain white powder, then ZnO powder is dispersed in butanol with a concentration of 10 mg/mL to deposit an electron transfer layer (ETL), and the n-type transport layer is obtained by spin coating at 4000 rpm for 60s and annealing for 10 min.

[0110] 5. A layer of C.sub.60 is grown on the basis of the previous step by using thermal evaporation technology at an evaporation rate of 0.2 ?/s as an n-type dense layer with a thickness of 20 nm.

[0111] 6. The solution is prepared by mixing the V.sub.2CTX powder prepared in the early stage with isopropanol at a mass ratio of 2:13, and then the solution is shaken on the vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 20 min, after fixing the substrate on the coating machine platform, the surface of the substrate is slowly pressed on the surface of the substrate by a four-sided preparation device, and then the load-bearing weight crank of the coating machine is slowly pressed on the top of the four-sided preparation. At the same time, anhydrous ether and n-hexane are poured into a square container at a ratio of 1:1 and mixed evenly. The mixed solution is coated on the upper edge of the substrate (50-75 ?L) by using a pipette, the coating machine is selected to work at a speed of 5 mm/s. After the coating is completed, the substrate with a wet film is quickly immersed in a mixed solution of ether and n-hexane for anti-solvent treatment for 2 min. And after that, the substrate is placed on a temperature-controlled heating stage and annealed at 150? C. for 30 min to prepare a tunneling junction film.

[0112] 7. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a p-type transport layer. 631 mg of PTAA is dissolved in 2 mL of chlorobenzene, the PTAA solution is dropped on the glass substrate and rotated at 2000 rpm for 20s, then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of about 20 nm.

[0113] 8. On the basis of the previous step, a layer of narrow band gap perovskite film is prepared, and the precursor solution of CsPb.sub.0.4Sn.sub.0.6I.sub.2Br is also prepared: in a nitrogen-filled glove box, CsI:(PbI.sub.2+PbBr.sub.2):(SnI.sub.2+SnBr.sub.2): SnF.sub.2 is weighed at a stoichiometric molar ratio of 1:0.4:0.6:0.1 and dissolved in an organic mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide (DMF:DMSO=3:7) to prepare a 1 mol/L precursor solution, after stirring at room temperature for 10-12 h, it is filtered by a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.22 ?m, and then 50 ?L of perovskite precursor solution is taken with a pipette, the perovskite precursor is dropped on the substrate, adjusted to 4000 rpm, and spin-coated for 30s. The spin-coated substrate is annealed at 120? C. on a heating stage for 10 min. A narrow band gap perovskite film with a thickness of about 300 nm is prepared.

[0114] 9. A layer of C.sub.60 and BCP is grown by thermal evaporation technology at 0.2 ?/s evaporation rate as an n-type transport layer, the thickness of C.sub.60 is 20 nm and the thickness of BCP is 7 nm.

[0115] 10. Finally, by using the thermal evaporation source, a layer of Au with a thickness of 100 nm is evaporated at a speed of 0.5 ?/s as a metal electrode.

Embodiment 6

[0116] This Embodiment 6 uses the structure shown in FIG. 1 (right) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0117] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15?20 min, and it is also put into the oven at 75? C., and then the cleaned conductive glass substrate is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0118] 2. A layer of SnO.sub.2 is prepared by chemical bath deposition (CBD) as an n-type transport layer. Firstly, SnCl.sub.2-2H.sub.2O mother liquor needs to be prepared. 5 g urea is dissolved in 400 mL deionized water, and then 100 ?L mercaptoacetic acid and 5 mL HCl (37 wt %) are added, finally, 1.096 g SnCl.sub.2-2H.sub.2O powder is dissolved into 0.012M solution, the solution is fully oscillated, mixed and placed in the refrigerator for three days. Then, the SnO.sub.2 layer is deposited, the cleaned ITO conductive glass is put into the UV cleaning machine for 15 min to remove the organic stains on the surface of the glass and improve the surface wettability. 200 ?L of standing SnCl.sub.2 2H.sub.2O mother liquor is mixed with 100 mL of deionized water to prepare a 0.02M diluent, and then the treated ITO substrate is immersed in the prepared diluent and placed in an oven at 60? C. for 1 h. After fully reacting, the solution is repeatedly rinsed with deionized water until it is clear and transparent, and then dried by air gun, the CBD steps are repeated twice to ensure the formation of a dense and appropriate thickness of SnO.sub.2 layer. Finally, n-type transport is obtained by annealing at 150? C. on a heating stage for 1 h.

[0119] 3. A layer of wide band gap perovskite film is deposited on the basis of the previous step. CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are prepared by dissolving 124 mg PbCl.sub.2 and 23 mg CH.sub.3 NH.sub.3I, 92 mg PbBr.sub.2 and 23 mg CH.sub.3NH.sub.3Br in 2 mL DMF solution respectively. Then CH.sub.3NH.sub.3PbI.sub.3 and CH.sub.3NH.sub.3PbBr.sub.3 solutions are mixed at a ratio of 3:2 to obtain CH.sub.3NH.sub.3Pb (I.sub.0.6Br.sub.0.4).sub.3 solution, and then 50 ?L solution is rotated at 4000 rpm for 60s, and annealed at 100? C. for 1 min, then annealed at 150? C. for 10 min to obtain a layer of wide band gap perovskite film with a thickness of about 300 nm.

[0120] 4. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a hole transport layer. 631 mg of PTAA is dissolved in 2 mL of chlorobenzene, and the PTAA solution is dropped on the glass substrate, rotated at 2000 rpm for 20s, and then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of 20 nm.

[0121] 5. A layer of NiO.sub.x is grown on the substrate by atomic layer deposition (ALD) as a p-type dense layer with a thickness of 10 nm.

[0122] 6. The solution is prepared by mixing the V.sub.2CT.sub.x powder prepared in the early stage with isopropanol at a mass ratio of 2:13, and the solution is shaken on the vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 20 min, after fixing the substrate on the coating machine platform, the surface of the substrate is slowly pressed by a four-sided preparation device, and then the load-bearing weight crank of the coating machine is slowly pressed on the top of the four-sided preparation. At the same time, anhydrous ether and n-hexane are poured into a square container at a ratio of 1:1 and mixed evenly. The mixed solution is coated on the upper edge of the substrate (50-75 ?L) by using a pipette, the coating machine is selected to work at a speed of 5 mm/s. After the coating is completed, the substrate with a wet film is quickly immersed in a mixed solution of ether and n-hexane for anti-solvent treatment for 2 min. And after that, the substrate is placed on a temperature-controlled heating stage and annealed at 150? C. for 30 min to prepare a tunneling junction film.

[0123] 7. A layer of fullerene (C.sub.60) is prepared by thermal evaporation as an n-type transport layer, the prepared substrate is transferred to the thermal evaporation chamber, and the C.sub.60 film layer is prepared by high vacuum evaporation coating machine. Firstly, the vacuum degree of the evaporation space is pumped below 10 Pa by a mechanical pump, and a secondary molecular pump is enabled to achieve a high vacuum environment, when the vacuum degree of the evaporation space reaches below 5?10.sup.?3 Pa, the deposition of 20 nm thin film is completed at an evaporation rate of 0.2 ?/s.

[0124] 8. On the basis of the prepared C.sub.60 layer, a layer of narrow band gap perovskite film is prepared, and the precursor solution of CsPb.sub.0.4Sn.sub.0.6I.sub.2Br is also prepared: in a nitrogen-filled glove box, CsI:(PbI.sub.2+PbBr.sub.2):(SnI.sub.2+SnBr.sub.2): SnF.sub.2 is weighed at a stoichiometric molar ratio of 1:0.4:0.6:0.1 and dissolved in an organic mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide (DMF:DMSO=3:7) to prepare a 1 mol/L precursor solution, after stirring at room temperature for 10-12 h, it is filtered by a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.22 ?m, and then 50 ?L of perovskite precursor solution is taken by a pipette, the perovskite precursor is dropped on the substrate, adjusted to 4000 rpm, and spin-coated for 30s. The spin-coated substrate is annealed at 120? C. on a heating stage for 10 min. A narrow band gap perovskite film with a thickness of about 300 nm is prepared.

[0125] 9. A layer of Spiro-OMeTAD is prepared by spin coating technology as a p-type transport layer. 520 mg of lithium bis (trifluoromethanesulfonyl) imide powder is added to 1 mL of acetonitrile (ACN), and the lithium salt solution is obtained by stirring at room temperature for 3 h in a magnetic stirrer until it is dissolved. Then 101 mg Spiro-OMeTAD, 34 ?L lithium salt, 25.4 ?L TBP solution and 1 ml chlorobenzene are added to a 3 mL glass bottle to prepare Spiro-OMeTAD hole transport layer solution, the spin coating instrument program is set to 5000 rpm for 30s, the 40 ?L Spiro-OMeTAD solution is weighed by a pipette, and the hole transport layer is prepared by dynamic spin-coating the hole solution on the perovskite film.

[0126] 10. Finally, by using the thermal evaporation source, a layer of Cu with a thickness of 120 nm is evaporated at a speed of 0.5 ?/s as a back electrode.

Embodiment 7

[0127] This Embodiment 7 uses the structure shown in FIG. 1 (left) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0128] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15 min, and it is also put into the oven at 80? C. for drying, and then the cleaned conductive glass substrate is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0129] 2. NiO.sub.x: 0.5 mol nickel nitrate hexahydrate is dissolved in 100 mL deionized water to obtain a dark green solution. NaOH solution (10 mol/L) is dropped into nickel nitrate hexahydrate solution until the pH value of the solution is 10. The colloidal precipitate is obtained by stirring at 40? C. for 10 min. The precipitate is washed twice with deionized water, dried at 80? C. for 6 h to obtain green powder, and calcined at 270? C. for 2 h to obtain dark black powder NiO.sub.x. NiO.sub.x and isopropanol are configured in a ratio of 3 mg:1 ml, and 80 ?L of NiO.sub.x aqueous solution is spin-coated on a cleaned ITO substrate at a speed of 3000 rpm/min for 30s. Then the sample is annealed at 110? C. for 20 min to obtain nickel oxide p-type transport layer.

[0130] 3. On the basis of the previous step, a wide band gap perovskite film is deposited, and the CsPbBr.sub.3 film is prepared by two-step deposition method. 1M PbBr.sub.2 is dissolved in 2 mL DMF solution, heated and stirred at 75? C. for 20 min, and then filtered with a 0.5 ?m polytetrafluoroethylene filter, a certain amount of solution is spin-coated on the substrate at a speed of 2500 rpm/min, and then annealed at 75? C. for 10 min. After cooling to room temperature, 1.5M CsBr is dissolved in 2 mL methanol solution, and a certain amount of solution is spin-coated on the substrate at a speed of 4500 rpm/min, and then annealed at 250? C. for 15 min. Thus, a layer of CsPbBr.sub.3 film is prepared.

[0131] 4. A layer of fullerene (C.sub.60) is prepared by thermal evaporation as an n-type transport layer, the prepared substrate is transferred to the thermal evaporation chamber, and the C.sub.60 film layer is prepared by high vacuum evaporation coating machine. Firstly, the vacuum degree of the evaporation space is filtered to below 10 Pa by a mechanical pump, and a secondary molecular pump is used to achieve a high vacuum environment, when the vacuum degree of the evaporation space reached below 5?10.sup.?3 Pa, the established evaporation process is started, and the deposition of 20 nm thin film is completed at an evaporation rate of 0.2 ?/s.

[0132] 5. A layer of SnO.sub.2 is prepared on the substrate by atomic layer deposition (ALD) as a n-type dense layer with a thickness of 20 nm.

[0133] 6. The solution is prepared by mixing the Ti.sub.3C.sub.2T.sub.x powder prepared in the early stage with isopropanol at a mass ratio of 2:7, and then the solution is shaken on the vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 15 min, then 70 ?L solution is taken to drop the composite layer solution on the glass substrate, and the rotation speed is set at 3500 rpm for 30s. The spin-coated glass is annealed on a heating stage at 60? C. for 15 min to obtain a tunneling junction composite layer.

[0134] 7. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a hole transport layer. 631 mg of PTAA is dissolved in 2 mL of chlorobenzene, the PTAA solution is dropped on the glass substrate and rotated at 2000 rpm for 20s, then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of about 20 nm.

[0135] 8. On the basis of the previous step, a layer of narrow band gap perovskite film is prepared, and the precursor solution of CsPb.sub.0.4Sn.sub.0.6I.sub.2Br is also prepared: in a nitrogen-filled glove box, CsI:(PbI.sub.2+PbBr.sub.2):(SnI.sub.2+SnBr.sub.2): SnF.sub.2 is weighed at a stoichiometric molar ratio of 1:0.4:0.6:0.1 and dissolved in an organic mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide (DMF:DMSO=3:7) to prepare a 1 mol/L precursor solution, after stirring at room temperature for 10-12 h, it is filtered by a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.22 ?m, and then 50 ?L of perovskite precursor solution is taken by using a pipette, the perovskite precursor is dropped on the substrate, adjusted to 4000 rpm, and spin-coated for 30s. The spin-coated substrate is annealed at 120? C. on a heating stage for 10 min. A narrow band gap perovskite film with a thickness of about 300 nm is prepared.

[0136] 9. A layer of C.sub.60 and BCP is grown by thermal evaporation technology at 0.2 ?/s evaporation rate as an n-type transport layer, the thickness of C.sub.60 is 20 nm and the thickness of BCP is 7 nm.

[0137] 10. Finally, by using the thermal evaporation source, a layer of Au with a thickness of 100 nm is evaporated at a speed of 0.5 ?/s as a metal electrode.

Embodiment 8

[0138] This Embodiment 8 uses the structure shown in FIG. 1 (right) to prepare perovskite/perovskite tandem solar cell, the specific preparation process is as follows:

[0139] 1. The ITO conductive glass substrate is put into the detergent, deionized water, isopropanol, anhydrous ethanol for conducting ultrasonic treatment 15?20 min, and it is also put into the oven at 75? C., and then the cleaned conductive glass substrate is placed in the ultraviolet-ozone device for 20 min to improve the surface wettability of the glass substrate and reduce the defects.

[0140] 2. A layer of SnO.sub.2 is prepared by chemical bath deposition (CBD) as an n-type transport layer. Firstly, SnCl.sub.2-2H.sub.2O mother liquor needs to be prepared. 5 g urea is dissolved in 400 mL deionized water, and then 100 ?L mercaptoacetic acid and 5 mL HCl (37 wt %) are added, finally, 1.096 g SnCl.sub.2-2H.sub.2O powder is dissolved into 0.012M solution, the solution is fully oscillated, mixed and placed in the refrigerator for three days. Then, the SnO.sub.2 layer is deposited, the cleaned ITO conductive glass is put into the UV cleaning machine for 15 min to remove the organic stains on the surface of the glass and improve the surface wettability. 200 ?L of standing SnCl.sub.2 2H.sub.2O mother liquor is mixed with 100 mL of deionized water to prepare a 0.02M diluent, and then the treated ITO substrate is immersed in the prepared diluent and placed in an oven at 60? C. for 1 h. After fully reacting, the solution is repeatedly rinsed with deionized water until it is clear and transparent, and then dried by air gun, the CBD steps are repeated twice to ensure the formation of a dense and appropriate thickness of SnO.sub.2 layer. Finally, n-type transport layer is obtained by annealing at 150? C. on a heating stage for 1 h.

[0141] 3. On the basis of the previous step, a wide band gap perovskite film is deposited, and the CsPbBr.sub.3 film is prepared by two-step deposition method. 1M PbBr.sub.2 is dissolved in 2 mL DMF solution, heated and stirred at 75? C. for 20 min, and then filtered with a 0.5 ?m polytetrafluoroethylene filter, a certain amount of solution is spin-coated on the substrate at a speed of 2500 rpm/min, and then annealed at 75? C. for 10 min. After cooling to room temperature, 1.5M CsBr is dissolved in 2 mL methanol solution, and a certain amount of solution is spin-coated on the substrate at a speed of 4500 rpm/min, and then annealed at 250? C. for 15 min. Thus, a layer of CsPbBr.sub.3 film is prepared.

[0142] 4. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) is used as a hole transport layer. 631 mg of PTAA is dissolved in 2 mL of chlorobenzene, and the PTAA solution is dropped on the glass substrate, rotated at 2000 rpm for 20s, and then the sample is annealed at 120? C. for 10 min to prepare a p-type transport layer with a thickness of 20 nm.

[0143] 5. A layer of NiO.sub.x is grown on the substrate by atomic layer deposition (ALD) as a p-type dense layer with a thickness of 10 nm.

[0144] 6. The solution is prepared by mixing the Ti.sub.3C.sub.2T.sub.x powder prepared in the early stage with isopropanol at a mass ratio of 2:7, and then the solution is shaken on the vortex machine for 5 min to ensure the uniform texture of the solution, and then the solution is conducted ultrasonic treatment for 15 min, then 70 ?L solution is taken to drop the composite layer solution on the glass substrate, and the rotation speed is set at 3500 rpm for 30s. The spin-coated glass is annealed on a heating stage at 60? C. for 15 min to obtain a tunneling junction composite layer.

[0145] 7. A layer of SnO.sub.2 is grown on the substrate by atomic layer deposition (ALD) as an n-type dense layer with a thickness of 10 nm.

[0146] 8. On the basis of the previous step, a layer of narrow band gap perovskite film is prepared, and the precursor solution of CsPb.sub.0.4Sn.sub.0.6I.sub.2Br is also prepared: in a nitrogen-filled glove box, CsI:(PbI.sub.2+PbBr.sub.2):(SnI.sub.2+SnBr.sub.2): SnF.sub.2 is weighed at a stoichiometric molar ratio of 1:0.4:0.6:0.1 and dissolved in an organic mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide (DMF:DMSO=3:7) to prepare a 1 mol/L precursor solution, after stirring at room temperature for 10-12 h, it is filtered by a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.22 ?m, and then 50 ?L of perovskite precursor solution is taken by using a pipette, the perovskite precursor is dropped on the substrate, adjusted to 4000 rpm, and spin-coated for 30s. The spin-coated substrate is annealed at 120? C. on a heating stage for 10 min. A narrow band gap perovskite film with a thickness of about 300 nm is prepared.

[0147] 9. A layer of Spiro-OMeTAD is prepared by spin coating technology as a p-type transport layer. 520 mg of lithium bis (trifluoromethanesulfonyl) imide powder is added to 1 mL of acetonitrile (ACN), and the lithium salt solution is obtained by stirring at room temperature for 3 h in a magnetic stirrer until it is dissolved. Then 101 mg Spiro-OMeTAD, 34 ?L lithium salt, 25.4 ?L TBP solution and 1 ml chlorobenzene are added to a 3 mL glass bottle to prepare Spiro-OMeTAD hole transport layer solution, the spin coating instrument program is set to 5000 rpm for 30s, the 40 ?L Spiro-OMeTAD solution is weighed by a pipette, and the hole transport layer is prepared by dynamic spin-coating the hole solution on the perovskite film.

[0148] 10. Finally, by using the thermal evaporation source, a layer of Au with a thickness of 100 nm is evaporated at a speed of 0.5 ?/s as a back electrode.