Method for co-doping and passivating a tin-based perovskite film by p-type material and application thereof

Abstract

The application belongs to the technical field of perovskite solar cells, and particularly relates to a method for doping and passivating a tin-based perovskite film by a P-type material and application thereof. The P-type material is dissolved in an organic solvent to prepare an additive solution, metal halide and organic ammonium halide are dissolved in an organic solvent to obtain a perovskite precursor solution, the additive solution is added to the perovskite precursor solution in a corresponding proportion to modify the perovskite precursor solution, and finally the perovskite precursor solution containing the additive is prepared into a uniform and dense tin-based perovskite film through various thin film deposition technologies. Meanwhile, the above method is applied to prepare a tin-based perovskite solar cell without a hole transport layer, which can reduce defects of the thin film, accelerate separation and transport of carriers, reduce the cost of device preparation, realize a high photoelectric conversion efficiency of more than 20%, and has good stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite solar cells, and particularly relates to a method for doping and passivating a tin-based perovskite film by a P-type material and application thereof. BACKGROUND

[0002] Solar energy, as a clean and renewable energy, is of great significance to solve the energy crisis, and thus is increasingly valued by people. In recent years, perovskite solar cells have become one of the most promising photovoltaic technologies due to their high photoelectric conversion efficiency and the advantage of simple solution preparation. At present, the photoelectric conversion efficiency (PCE) of perovskite solar cells has rapidly increased from 3.8% to 25.7% certified efficiency, which can be comparable to traditional crystalline silicon solar cells.

[0003] At present, high-efficiency perovskite solar cells mainly use traditional lead-based perovskite materials. However, the traditional lead-based perovskite material contains lead elements, and the toxicity of lead elements and their pollution to the environment have become the main obstacles to the commercial application of perovskite solar cells. Therefore, the research on lead-poor or lead-free perovskite solar cells has gradually become a research hotspot in the field of photovoltaic technology. Subsequently, tin (Sn) -based, silver (Ag) -based, antimony (Sb) -based, bismuth (Bi) -based, copper (Cu) -based and germanium (Ge) -based halide perovskite solar cells have been gradually reported. Among them, tin, which is in the same main group as lead and has less toxicity, is one of the most potential choices. The ionic radius of Sn 2+ is slightly smaller than that of Pb 2+ Therefore, it can replace lead and retain the perovskite structure. At the same time, tin-based perovskite has a narrower optical band gap, lower exciton binding energy and higher carrier mobility. It is worth mentioning that the band gap of tin-containing perovskite material can be adjusted between 1.1-1.4 eV, which is expected to make the efficiency of perovskite solar cells break through the Shockley-Queisser limit. However, the highest efficiency of pure tin-based perovskite solar cells is only 14.81%, which is far behind lead-based perovskite solar cells. The main reasons for this situation are as follows: first, the crystallization speed of tin-based perovskite is too fast, resulting in a rough film surface, low crystallinity and many defects; second, Sn 2+ is very unstable and easily oxidized to Sn 4+ , thereby causing severe p-type doping and increasing the defect state density.

[0004] Compared with pure tin-based perovskite solar cells, tin-lead mixed perovskite solar cells exhibit more excellent photoelectric performance and better stability. The energy band of tin-lead mixed perovskite can be adjusted between 1.2-1.55eV, making it an ideal light absorption material close to the Shockley-Queisser limit. However, like pure tin-based perovskite, binary tin-lead mixed perovskite also faces the problem of high defect density caused by the easy oxidation of Sn 2+ In addition, the reaction competition between tin, lead and organic amine during the formation of tin-lead mixed perovskite thin film also increases the difficulty of preparing high-quality thin film.

[0005] Meanwhile, in the traditional perovskite solar cell structure, a hole transport layer is needed to block electrons, enhance hole transport, and prevent direct contact between the perovskite active layer and the electrode, which can cause leakage or device short circuit. However, there are still some problems with the hole transport layer for tin-based perovskite solar cells, such as expensive materials, complex preparation process, low hole mobility, poor optical performance, poor contact with perovskite layer, and mismatched energy levels. Although there have been reports on tin-based perovskite solar cells without a hole transport layer, current technology still mainly focuses on improving the oxidation resistance of tin-based perovskite, and there are few reports on improving the energy level matching between perovskite and conductive substrate.

[0006] In summary, in view of the problems of tin-based perovskite thin film, such as high defect density, poor compatibility with existing hole transport layers, and mismatched energy levels between conductive substrate and perovskite in devices without a hole transport layer, it is necessary to develop a new type of collaborative doping and passivation method for tin-based perovskite thin film. The method can passivate the defects of tin-based perovskite thin film, improve the energy level matching between perovskite and conductive substrate, promote the separation and transport of carriers, and prepare high-efficiency and stable tin-based perovskite solar cells without a hole transport layer, while simplifying the manufacturing process and reducing the manufacturing cost. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a method for collaborative doping and passivation of tin-based perovskite thin film by P-type material, which uses P-type material (also known as P-type semiconductor material) as an additive and prepares perovskite precursor solution to modify perovskite material, reduce thin film defects, and reduce device manufacturing cost, so that it can be applied to the preparation of simple, efficient and low-toxic tin-based perovskite solar cell devices without a hole transport layer (HTL-free).

[0008] To achieve the above purpose, the present application is realized by the following technical scheme:

[0009] The present application provides a method for collaborative doping and passivation of tin-based perovskite thin film by P-type material, which comprises the following steps:

[0010] S1, dissolving a P-type material in an organic solvent to prepare an additive solution;

[0011] S2, dissolving a metal halide and an organic ammonium halide in an organic solvent to prepare a perovskite precursor solution of tin-based ABX3, wherein A is a mixture of one or more of Cs + , Rb + and monovalent organic cations including methylamine ions, formamidine ions, B is a mixture of Sn 2+ or Sn 2+ and Pb 2+ , and X is a mixture of one or more of Cl - , Br - , I - , SCN - ;

[0012] S3, adding the additive solution of step S1 to the tin-based perovskite ABX3 precursor solution of step S2, then using the obtained ABX3 precursor solution to prepare a tin-based perovskite thin film on a conductive substrate after film formation and annealing.

[0013] Preferably, the P-type material includes 2PACz ([2-(9H-carbazole-9-yl) ethyl] phosphonic acid), 4PACz ([2-(9H-carbazole-9-yl) butyl] phosphonic acid), 6PACz ([2-(9H-carbazole-9-yl) hexyl] phosphonic acid), Me-4PACz ([4-(3,6-dimethyl-9H-carbazole-9-yl) butyl phosphonic acid), MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazole-9-yl) ethyl] phosphonic acid), F4TCNQ (2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane), F6TCNQ (2,2-(perfluoronaphthalene-2,6-diylidene) diformonitrile). Specifically, the P-type material is 2PACz.

[0014] The present application first dissolves a P-type material in an organic solvent to prepare an additive solution, then dissolves a metal halide and an organic ammonium halide in an organic solvent to obtain a perovskite precursor solution, then adds the additive solution to the perovskite precursor solution in a corresponding proportion to modify it, and finally prepares a uniform and dense tin-based perovskite thin film from the perovskite precursor solution containing the additive by a film formation method, to reduce defects in the thin film, accelerate the separation and transport of carriers, and realize the preparation of a high photoelectric conversion efficiency tin-based perovskite solar cell device without a hole transport layer (HTL-free).

[0015] Preferably, the P-type material is dissolved in the additive solution at a molar concentration of 0.05-2M.

[0016] Preferably, the additive solution is added in an amount of 0.5-10% of the volume of the tin-based perovskite ABX3 precursor solution. In particular, the additive solution is added in an amount of 1% of the volume of the tin-based perovskite ABX3 precursor solution.

[0017] Preferably, the organic solvent in step S2 is the same as the organic solvent in step S1.

[0018] Further, the organic solvent is selected from one or more of a mixture of DMSO (dimethyl sulfoxide), DMF (N,N-dimethylformamide), MF (methyl formate), DMAC (dimethylacetamide), 2-ME (glycol methyl ether), NMF-1 (N-methyl formamide-1), NMF-2 (N-methyl formamide-2), and NMP (1-methyl 2-pyrrolidine).

[0019] Still further, the organic solvent is a mixed solution of DMSO and DMF, and the volume ratio of DMF to DMSO is 3:1, 4:1, or 7:3.

[0020] Preferably, the film-forming method includes a gas-blowing assisted spin coating method, a thermal blade coating method, an anti-solvent assisted spin coating method, a slot coating method, a drop coating method, and a spray coating method.

[0021] Further, the gas-blowing assisted spin coating method has a rotation speed of 2000 rpm-10000 rpm, uses an inert gas such as nitrogen, argon, or helium for blowing, and has an operating temperature range of 10-70°C. The thermal blade coating method has an operating temperature of 10-150°C. The gas-blowing assisted blade coating method uses an inert gas such as nitrogen, argon, or helium for blowing and has an operating temperature range of 25-70°C. The anti-solvent assisted spin coating method has a rotation speed of 2000 rpm-10000 rpm and an operating temperature of 10-30°C.

[0022] Still further, for the anti-solvent assisted spin coating method, the anti-solvent is selected from a mixture of one or more of methanol, ethanol, n-propanol, isopropanol, butanol, isobutanol, 2-butanol, amyl alcohol, isoamyl alcohol, ethylene glycol, glycerol, acetone, butanone, methyl ether, anisole, diethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, acetonitrile, acrylonitrile, chloroform, chlorobenzene, dichlorobenzene, toluene, m-xylene, mesitylene, trifluorotoluene, ethyl acetate, carbon tetrachloride, dichloroethane, carbon disulfide, and cyclohexane. In particular, the anti-solvent is chlorobenzene.

[0023] Preferably, the annealing is one-step annealing or two-step annealing. The one-step annealing has a temperature of 80-150°C and an annealing time of 1-60 minutes. The two-step annealing first has an annealing temperature of 50-90°C and an annealing time of 5-30 minutes, and then has an annealing temperature of 90-150°C and an annealing time of 5-30 minutes.

[0024] Preferably, the conductive substrate includes fluorine-doped tin dioxide (FTO) conductive glass, indium-doped tin dioxide (ITO) conductive glass, or flexible conductive plastic (PET / ITO, PEN / ITO), etc.

[0025] The application also provides an application of the above method for cooperatively doping and passivating a tin-based perovskite film by a P-type material in the preparation of a solar cell.

[0026] The application cooperatively dopes and passivates the perovskite material by using a P-type material, while reducing the defect density of the film, thereby preparing a tin-based solar cell without a hole transport layer (HTL-free), reducing the cost of device manufacturing, and achieving a photoelectric conversion efficiency of >20% and good stability.

[0027] The application also provides a preparation method of a solar cell without a hole transport layer based on a P-type material-doped tin-based perovskite film, that is, first preparing a P-type material-doped tin-based perovskite film by using the above method for cooperatively doping and passivating a tin-based perovskite film by a P-type material, and then assembling the P-type material-doped tin-based perovskite film with an electron transport layer and a top electrode to form a solar cell without a hole transport layer based on a P-type material-doped tin-based perovskite film.

[0028] Preferably, the electron transport layer is in a dense or mesoporous structure, and the electron transport layer can be any one of fullerene and its derivatives (C 60 , bis-C 60 , PCBM, ICBA, etc.), and oxides or hydroxides of Ti 4+ , Sn 4+ , Zn 2+ , Nb 5+ , Al 3+ , etc.

[0029] Preferably, the top electrode is a metal material with a high work function, including but not limited to gold (Au), silver (Ag), copper (Cu), aluminum (Al), or a conductive carbon material; the conductive carbon material includes but is not limited to carbon nanoparticles, carbon black, carbon nanotubes, graphene, graphyne, and mixtures thereof.

[0030] Compared with the prior art, the application has the following beneficial effects:

[0031] The application discloses a method for doping and passivating a tin-based perovskite film by a P-type material, in which a P-type material is dissolved in an organic solvent to prepare an additive solution, metal halides and organic ammonium halides are dissolved in an organic solvent to obtain a perovskite precursor solution, then the additive solution is added into the perovskite precursor solution in a corresponding proportion to modify the perovskite precursor solution, and finally, the perovskite precursor solution containing the additive is prepared into a uniform and dense tin-based perovskite film by a film forming method. Meanwhile, the P-type material doped tin-based perovskite film prepared by the method can be used to prepare a hole transport layer (HTL-free) tin-based perovskite solar cell together with an electron transport layer and a top electrode. The method for doping and passivating the perovskite material by using the P-type material as an additive to prepare the perovskite precursor solution can reduce defects of the film, accelerate separation and transport of carriers, and be applied to preparation of a simple, efficient and low-toxic hole transport layer (HTL-free) tin-based perovskite solar cell device, so that the device manufacturing cost can be reduced, and a high photoelectric conversion efficiency of more than 20% and good stability can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 SEM images of tin-lead mixed perovskite films prepared by directly spin-coating a precursor solution (a, without 2PACz doping and passivation; b, with 2PACz doping and passivation);

[0033] Figure 2 XRD images of tin-lead mixed perovskite films prepared by directly spin-coating a precursor solution;

[0034] Figure 3 UPS images of tin-lead mixed perovskite films prepared by directly spin-coating a precursor solution (a, b, without 2PACz doping and passivation; c, d, with 2PACz doping and passivation);

[0035] Figure 4 Energy level diagrams of tin-lead mixed perovskite films prepared by directly spin-coating a precursor solution (control, w / o 2PACz) and modification (with 2PACz);

[0036] Figure 5 SEM images of tin-lead mixed perovskite films prepared by a blowing-assisted spin-coating method;

[0037] Figure 6 Device structure diagram of a hole transport layer-free solar cell based on a P-type material doped tin-lead mixed perovskite film;

[0038] Figure 7 J-V curve of a hole transport layer-free solar cell;

[0039] Figure 8J-V curves of hole-only devices in dark state. DETAILED DESCRIPTION

[0040] The specific embodiments of the present application will be further described below. It should be noted that the description of these embodiments is intended for the purpose of illustrating the present application and is not intended to limit the present application. Moreover, the technical features involved in each of the embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0041] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0042] Example 1 A method for co-doping and passivating a tin-lead mixed perovskite film with P-type material 2PACz

[0043] The film forming method of the present embodiment employs a spin coating method, which specifically includes the following steps:

[0044] (1) Select 2PACz ([2-(9H-carbazol-9-yl) ethyl] phosphonic acid) as the raw material of the additive solution, dissolve it in a DMF solution, and configure it into an additive solution of 0.5-2M;

[0045] (2) Dissolve CsI, MAI (methylammonium iodide), FAI (formamidinium iodide), PbI2, SnI2, and SnF2 in a DMSO and DMF mixed solution (the volume ratio of DMF to DMSO is 7:3) according to a molar ratio of 0.05:0.45:0.5:0.5:0.5:0.05, stir at room temperature for 4 hours, stir until the solids are dissolved and the solution is clear, and configure to obtain a 1.6M tin-lead mixed perovskite precursor solution 1;

[0046] (3) Add the additive solution (1% of the volume of the tin-lead mixed perovskite precursor solution) to the tin-lead mixed perovskite precursor solution 1, and filter to obtain a precursor solution 2;

[0047] (4) Spread the precursor solution 1 and the precursor solution 2 on conductive glass ITO using an anti-solvent assisted spin coating method, the spin coating speed is 6000 rpm / min, the spin coating time is 50s, the anti-solvent is chlorobenzene (sprayed from 15s to 45s), and annealing is performed at 100°C for 10min, to respectively prepare Cs 0.05 MA 0.45 FA 0.5 Sn 0.5 Pb 0.5 I3 tin-lead mixed perovskite control film and modified film.

[0048] The tin-lead mixed perovskite control film and the modified film were characterized by scanning electron microscopy (SEM), such as... Figure 1 As shown in the film morphology, it can be seen that the grain size of both the control film and the modified film is about 500 nm. However, there are white flake-like precipitates at the grain boundaries of the control film, while no precipitates appear at the grain boundaries of the tin-lead mixed perovskite film doped and modified by P-type material.

[0049] Meanwhile, XRD diffraction patterns of the tin-lead mixed perovskite control film and the modified film were further analyzed. Figure 2 As shown, both films exhibit diffraction peaks at the (110), (202), (220), and (310) crystal planes. The control film shows a distinct PbI2 / SnI2 diffraction peak at 12.65°, corresponding to the white precipitates in the SEM image. However, the perovskite film doped and modified with P-type material 2PACz not only shows a significant increase in crystallinity but also exhibits no diffraction peak at 12.65°. This indicates that P-type material 2PACz can improve the crystallinity of the perovskite film and suppress the precipitation of PbI2 or SnI2, thereby reducing film defects.

[0050] Furthermore, ultraviolet photoelectron spectroscopy (UPS) analysis was performed on the tin-lead mixed perovskite control film and the modified film. Figure 3 As shown, the Fermi level of the perovskite film decreased from -4.89 eV in the control sample to -5.01 eV in the modified sample, proving that the addition of 2PACz caused p-type doping of the perovskite film. Figure 4 For comparison of the energy level diagrams of the thin film and the modified thin film, it can be seen that after co-doping and passivation with p-type material 2PACz, the energy levels of the perovskite thin film and the conductive glass ITO are more matched, which is beneficial to the separation and transport of charge carriers.

[0051] Example 2: A method for co-doping and passivating tin-lead mixed perovskite thin films using p-type material 2PACz.

[0052] The specific preparation method is the same as in Example 1, except that the film formation method in this example is air-blowing assisted spin coating. That is, spin coating is used to prepare Cs. 0.05 MA 0.45 FA 0.5 Sn 0.5 Pb 0.5 Nitrogen gas blowing is used during the I3-modified film process at an operating temperature of 25°C. Nitrogen blowing accelerates the rapid evaporation of DMF / DMSO solvents, thereby achieving Cs... 0.05 MA 0.45 FA 0.5 Sn 0.5 Pb 0.5 Uniform coverage of the I3 thin film on the ITO substrate. Cs in this embodiment...0.05 MA 0.45 FA 0.5 Sn 0.5 Pb 0.5 The microstructure of the I3 modified film is as follows: Figure 5 As shown in the figure, the tin-lead mixed perovskite film prepared in this embodiment has a uniform grain size distribution and high coverage.

[0053] Example 3: Application of the method of co-doping of P-type material 2PACz and passivation of tin-lead mixed perovskite thin film in the fabrication of hole transport layer-free solar cell devices.

[0054] The structure of the solar cell device is as follows: Figure 6 As shown, from bottom to top, it includes an ITO conductive glass substrate, a modified tin-lead mixed perovskite film doped and passivated with P-type material prepared in Example 1, and an electron transport layer (C). 60 BCP and Cu electrodes. The specific preparation method includes the following steps:

[0055] (1) Place the ITO conductive glass substrate in deionized water, acetone and isopropanol in sequence, ultrasonically clean for 20 minutes each, dry in an oven, and then treat with a UV ozone cleaner for 25 minutes.

[0056] (2) Spin-coat the precursor solution 2 prepared in Example 1 onto the ITO conductive substrate at a spin speed of 6000 rpm / min and a spin time of 50 s. Spray the anti-solvent chlorobenzene (CB) at an appropriate time (15-45 s) to obtain a tin-lead mixed perovskite layer with a thickness of 600 nm. Finally, anneal the obtained tin-lead mixed perovskite layer at 100 °C for 10 min.

[0057] (3) At a vacuum degree of 5×10 -4 Under vacuum conditions of Pa, 20 nm of C was deposited on the perovskite surface by vapor deposition. 60 A hole transport layer-free solar cell device based on a tin-lead hybrid perovskite thin film doped with P-type material was fabricated using a 7nm BCP and a 100nm Cu electrode.

[0058] Meanwhile, the precursor solution 1 from Example 1 was prepared into a hole-transport layer-free solar cell device based on a control thin film using the same method.

[0059] The fabricated solar cell device was subjected to JV testing. Figure 7 It can be seen that the photoelectric conversion efficiency of the solar cell device directly prepared from precursor solution 1 is only about 15%, while the open-circuit voltage V of the tin-lead hybrid perovskite solar cell device prepared from precursor solution 2 is much higher. OC Short-circuit current JSC , the fill factor FF is improved, and the photoelectric conversion efficiency (PCE) is more than 20%, so it can be applied to solar cell devices. The tin-lead mixed perovskite film doped and passivated by the P-type material 2PACz is prepared into an ITO / PTAA / perovskite / spiro / Cu device. PTAA and spiro are prepared by spin coating, and the Cu electrode is obtained by vacuum evaporation. The defect density change before and after adding the additive is estimated by the space charge limited current method. The defect density of the perovskite film before and after adding the additive is calculated by the defect filling voltage. Figure 8 It can be seen that the defect density calculated by the defect filling voltage is reduced from 1.10×10 16 cm -3 to 6.48×10 15 cm -3 , which shows that after the modification of the P-type material 2PACz, the defect density of the perovskite film is greatly reduced, that is, the film quality is effectively improved.

[0060] The above describes the embodiments of the present application, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments without departing from the principles and spirits of the present application still fall within the protection scope of the present application.

Claims

1. A method for preparing a hole transport layer-free solar cell based on a tin-based perovskite thin film doped with a P-type material, characterized in that, The P-type material doped tin-based perovskite thin film is prepared according to the method of "doping and passivating tin-based perovskite thin film by P-type material", and then assembled with an electron transport layer and a top electrode to form a hole transport layer-free solar cell based on the P-type material doped tin-based perovskite thin film. The method of "doping and passivating tin-based perovskite thin film by P-type material" comprises the following steps: S1, dissolving P-type material in an organic solvent to prepare an additive solution, wherein the P-type material is 2PACz; S2, dissolving the metal halide and the organic ammonium halide in an organic solvent to form a perovskite ABX3 precursor solution, wherein A is a mixture of one or more of Cs + , Rb + and a monovalent organic cation comprising a methylamine ion, a formamidinium ion, B is a mixture of Sn 2+ or Sn 2+ and Pb 2+ , and X is a mixture of one or more of Cl - , Br - , I - , SCN - ; S3, adding the additive solution of step S1 to the tin-based perovskite ABX3 precursor solution of step S2, then using the obtained ABX3 precursor solution to perform film formation and annealing on a conductive substrate to prepare a tin-based perovskite thin film.

2. The method of claim 1, wherein the method is characterized by: The molar concentration of the P-type material dissolved in the additive solution is 0.05-2M.

3. The method of claim 1, wherein the method is characterized by: The additive solution is added in an amount of 0.5-10% of the volume of the tin-based perovskite ABX3 precursor solution.

4. The method of claim 1, wherein the method is characterized by: The organic solvent of step S2 is the same as the organic solvent of step S1.

5. The method of claim 4, wherein the method is characterized by: The organic solvent is selected from a mixture of one or more of DMSO, DMF, MF, DMAC, 2-ME, NMF-1, NMF-2 and NMP.

6. The method of claim 1, wherein the method is characterized by: The film formation method comprises air-assisted spin coating, thermal blade coating, anti-solvent assisted spin coating, slot coating, drop coating and spraying.

7. The method of claim 1, wherein the method is characterized by: The annealing adopts one-step annealing or two-step annealing, the one-step annealing is performed at a temperature of 80-150℃ for 1-60 minutes, and the two-step annealing is first annealed at 50-90℃ for 5-30 minutes, and then annealed at 90-150℃ for 5-30 minutes.

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