Preparation method of stabilized perovskite absorption layer

Abstract

The invention provides a preparation method of a stabilized perovskite absorption layer, and belongs to the technical field of perovskite solar cells, and the preparation method comprises the following steps: S1, preparing a perovskite wet film through a one-step method or a two-step method; s2, carrying out first heat treatment on the perovskite thin film to obtain a perovskite thin film; wherein the heat preservation temperature of the first heat treatment is T1; s3, preparing an optimization layer solution containing Cl <-> and / or Br <->, and coating the surface of the perovskite thin film with the optimization layer solution to form an optimization layer solution film; and S4, the perovskite thin film and the optimization layer solution film are subjected to second heat treatment, a stabilized perovskite absorption layer is obtained, the stabilized perovskite absorption layer comprises a three-dimensional perovskite thin film and a two-dimensional perovskite thin film, the heat preservation temperature of the second heat treatment is T2, and T2 is larger than or equal to T1. According to the preparation method, the preparation of the stabilized perovskite absorption layer is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of perovskite solar cells, and in particular relates to a method for preparing a stabilized perovskite absorption layer. Background Art

[0002] Perovskite solar cells are a revolutionary new photovoltaic technology, selected by the US magazine Science as one of the top ten global technological breakthroughs in 2013. They have the characteristics and advantages of high efficiency, low cost, and can be prepared by low-temperature solution method. After just over a decade of development, perovskite solar cells have become the hottest branch of next-generation photovoltaic technology, attracting great attention and R&D investment from domestic and foreign academic and industrial circles.

[0003] The perovskite composition is ABX3, which has the characteristics of adjustable composition, and the type and content of elements A and X can usually be adjusted. Generally speaking, the X position is iodine (I), and the adjusted element is often chlorine (Cl), bromine (Br), etc. The adjustment of the X element type can adjust the band gap of the perovskite layer, etc.

[0004] For large-scale preparation of perovskite layers, doping with chlorine (Cl) or bromine (Br) elements will make the perovskite composition complicated, and complex compositions are often prone to component segregation and film formation difficulties. Therefore, it is urgent to design a preparation method for a stabilized perovskite absorber layer. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the embodiments of the present invention provide a method for preparing a stabilized perovskite absorber layer, which intervenes in the crystallization process of the perovskite film, optimizes the crystallization of the perovskite film, and realizes the preparation of a more stabilized perovskite absorber layer.

[0006] An embodiment of the present invention provides a method for preparing a stabilized perovskite absorption layer, comprising the following steps:

[0007] S1. Preparation of perovskite wet film by one-step or two-step method;

[0008] S2. performing a first heat treatment on the perovskite film to obtain a perovskite film; wherein the holding temperature of the first heat treatment is T1;

[0009] S3. Prepare Cl - and / or Br - The optimized layer solution is coated on the surface of the perovskite film to form an optimized layer solution film;

[0010] S4. Perform a second heat treatment on the perovskite film and the optimized layer solution film to obtain a stabilized perovskite absorption layer, wherein the stabilized perovskite absorption layer includes a three-dimensional perovskite film and a two-dimensional perovskite film, wherein the insulation temperature of the second heat treatment is T2, and T2 is greater than or equal to T1.

[0011] The advantages and technical effects brought by the preparation method of the embodiment of the present invention are:

[0012] (1) The embodiment of the present invention intervenes in the crystallization process of the perovskite absorber layer, optimizes the crystallization of the perovskite absorber layer through a chemical + thermodynamic coupling method, and realizes the preparation of a stabilized perovskite absorber layer.

[0013] (2) In the preparation method of the embodiment of the present invention, steps S3 and S4 allow chlorine (Cl) element and / or bromine (Br) element to replace part of the iodine (I) element on the surface of the perovskite film, thereby optimizing the perovskite film. Compared with ABI3, the perovskite material doped with chlorine (Cl) element and / or bromine (Br) element is more stable.

[0014] (3) In the preparation method of the embodiment of the present invention, step S4 realizes the passivation of the surface of the perovskite film, forming an iodide-rich two-dimensional perovskite film and a Cl and / or Br halide gradient extending from the defective surface and grain boundary to the three-dimensional layer of the body (that is, part of the I element in the three-dimensional perovskite film is replaced by Cl and / or Br, and the degree of replacement is often higher the closer to the two-dimensional perovskite film). The presence of the two-dimensional perovskite film and the Cl and / or Br halide gradient is beneficial to the optimization of the interface between the stabilized perovskite absorption layer and the charge transport layer, which can extend the carrier lifetime and reduce the interface recombination.

[0015] (4) In the preparation method of the embodiment of the present invention, T2 of step S4 is greater than or equal to T1 of step S2, so that a two-dimensional perovskite film can be grown on the surface of the three-dimensional perovskite film, thereby improving the photoelectric conversion efficiency of the perovskite solar cell.

[0016] In some embodiments, in step S2, T1 is 110-130°C.

[0017] In some embodiments, in step S3, the solute in the optimization layer solution is ammonium chloride and / or ammonium bromide.

[0018] In some embodiments, in step S3, the molar concentration of ammonium chloride and / or ammonium bromide in the optimization layer solution is 0.01-0.3 mol / L.

[0019] In some embodiments, in step S3, the solvent in the optimization layer solution is a combination of isopropanol and / or chlorobenzene and N,N-dimethylformamide.

[0020] In some embodiments, in step S3, the ratio of N,N-dimethylformamide in the optimization layer solution is 1-5 wt %.

[0021] In some embodiments, in step S4, T2 is 140-160°C.

[0022] In some embodiments, in step S4, T2 is greater than T1. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic flow chart of steps S3 and S4 of the preparation method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0025] An embodiment of the present invention provides a method for preparing a stabilized perovskite absorption layer, comprising the following steps:

[0026] S1. Preparation of perovskite wet film by one-step or two-step method;

[0027] S2. performing a first heat treatment on the perovskite film to obtain a perovskite film; wherein the holding temperature of the first heat treatment is T1;

[0028] S3. Figure 1 As shown, the Cl - and / or Br - The optimized layer solution is coated on the surface of the perovskite film to form an optimized layer solution film;

[0029] S4. Figure 1 As shown, the perovskite film and the optimized layer solution film are subjected to a second heat treatment to obtain a stabilized perovskite absorption layer, wherein the stabilized perovskite absorption layer includes a three-dimensional perovskite film and a two-dimensional perovskite film, wherein the insulation temperature of the second heat treatment is T2, and T2 is greater than or equal to T1.

[0030] Working principle: The embodiment of the present invention intervenes in the crystallization process of the perovskite absorption layer, optimizes the crystallization of the perovskite absorption layer through the chemical + thermodynamic coupling method, and realizes the preparation of the stabilized perovskite absorption layer. Steps S3 and S4 allow the chlorine (Cl) element and / or bromine (Br) element to replace part of the iodine (I) element on the surface of the perovskite film, thereby optimizing the perovskite film. Compared with ABI3, the perovskite material doped with chlorine (Cl) element and / or bromine (Br) element is more stable.

[0031] In the preparation method of the embodiment of the present invention, step S4 realizes the passivation of the surface of the perovskite film, forms a two-dimensional perovskite film rich in iodide and a Cl and / or Br halide gradient extending from the defective surface and grain boundary to the three-dimensional layer of the body (that is, part of the I element in the three-dimensional perovskite film is replaced by Cl and / or Br, and the closer to the two-dimensional perovskite film, the higher the degree of replacement). The presence of the two-dimensional perovskite film and the Cl and / or Br halide gradient is conducive to the optimization of the interface between the stabilized perovskite absorption layer and the charge transport layer, which can extend the carrier lifetime and reduce the interface recombination. T2 of step S4 is greater than or equal to T1 of step S2, and a two-dimensional perovskite film can be grown on the surface of the three-dimensional perovskite film, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. Preferably, in some embodiments, in step S4, T2 is greater than T1. If T2 of step S4 is less than T1 of step S2, it is not possible to achieve a good growth of a two-dimensional perovskite film on the surface of the three-dimensional perovskite film.

[0032] Figure 1 It is a schematic flow chart of steps S3 and S4 of the preparation method of an embodiment of the present invention. It should be noted that the perovskite film and the optimized layer solution film are closely combined. Figure 1 The perovskite film and the optimized layer solution film are shown separated from each other only to clarify the preparation process. Similarly, the two-dimensional perovskite film and the three-dimensional perovskite film are also tightly combined, and the perovskite absorption layer composed of them has no obvious interface. Figure 1 The perovskite film and optimized layer solution film are shown separated from each other only to clarify the preparation process.

[0033] In some embodiments, in step S2, T1 is 110-130°C, such as 110°C, 102°C, 104°C, 106°C, 108°C, 110°C, etc. The first heat treatment is beneficial to the rearrangement and stabilization of the crystals, thereby improving the stability of the perovskite film.

[0034] In some embodiments, in step S3, the solute in the optimization layer solution is ammonium chloride and / or ammonium bromide. Ammonium chloride and / or ammonium bromide react with the perovskite ABI3, and the chlorine (Cl) element and / or bromine (Br) element replace part of the iodine (I) element on the surface of the perovskite film, thereby optimizing the perovskite film. Compared with ABI3, the perovskite material doped with chlorine (Cl) element and / or bromine (Br) element is more stable.

[0035] In some embodiments, in step S3, in the optimization layer solution, the molar concentration of the ammonium chloride and / or ammonium bromide is 0.01 to 0.3 mol / L, for example, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, etc. When the molar concentration of the ammonium chloride and / or ammonium bromide in the optimization layer solution is too low, it is not conducive to passivation of the surface of the perovskite film, forming a two-dimensional perovskite film rich in iodide and a Cl and / or Br halide gradient extending from the defective surface and grain boundary to the three-dimensional layer of the body, thereby not conducive to improving the stability of the perovskite absorption layer. When the molar concentration of the ammonium chloride and / or ammonium bromide in the optimization layer solution is too high, the content of the chlorine (Cl) element and / or bromine (Br) element doped in the perovskite absorption layer is too much, which is not conducive to maintaining a high photoelectric conversion efficiency.

[0036] In some embodiments, in step S3, the solvent in the optimization layer solution is a combination of isopropanol and / or chlorobenzene and N,N-dimethylformamide (DMF). The above types of solvents can dissolve ammonium chloride and / or ammonium bromide, so that the formed optimization layer solution is evenly coated on the surface of the perovskite film to form a film.

[0037] In some embodiments, in step S3, in the optimization layer solution, the ratio of N,N-dimethylformamide is 1-5wt%, such as 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, etc. When the ratio of N,N-dimethylformamide in the optimization layer solution is too low, the quality of the three-dimensional perovskite film will be significantly damaged. When the ratio of N,N-dimethylformamide in the optimization layer solution is too high, a good two-dimensional perovskite film cannot be formed.

[0038] In some embodiments, in step S4, T2 is 140-160°C, for example, 140°C, 145°C, 150°C, 155°C, 160°C, etc. When the holding temperature of the second heat treatment is too low, it is not conducive to the formation of stable phase perovskite. When the holding temperature of the second heat treatment is too high, it is not conducive to the uniform nucleation and crystallization process.

[0039] Example 1

[0040] (1) A 60 nm thick tin oxide film was vapor deposited on a 2 cm×2 cm FTO conductive glass after washing and drying, and then annealed to obtain a tin oxide electron transport layer, wherein the annealing temperature was 270° C. and the insulation time was 30 min.

[0041] (2) Dissolve PbI2 in DMF to form Pb 2+A PbI2 solution with a concentration of 1 mol / L; dissolving methyl ammonium iodide (MAI, CH3NH3I) in DMF to form I - The concentration of MAI solution is 1.25 mol / L. PbI2 solution is spin-coated on the surface of the tin oxide electron transport layer obtained in step (1) to form a PbI2 film, and then MAI solution is spin-coated on the surface of the PbI2 film to react and generate a 500 nm thick perovskite (CH3NH3PbI3) wet film. The perovskite (CH3NH3PbI3) wet film is then subjected to a first heat treatment to obtain a perovskite (CH3NH3PbI3) thin film, wherein the first heat treatment has a holding temperature T1 = 120°C and a holding time of 60 min.

[0042] (3) dissolving ammonium chloride in a mixed solution of isopropanol and DMF to obtain an optimized layer solution, wherein the molar concentration of ammonium chloride in the optimized layer solution is 0.15 mol / L, and the mass concentration of N,N-dimethylformamide in the optimized layer solution is 1-5%.

[0043] The optimized layer solution is spin-coated on the surface of the perovskite (CH3NH3PbI3) film to form an optimized layer solution film.

[0044] (4) The perovskite film and the optimized layer solution film are subjected to a second heat treatment, and ammonium chloride reacts with CH3NH3PbI3 to obtain a stabilized perovskite absorption layer. The stabilized perovskite absorption layer is a three-dimensional perovskite film and a two-dimensional perovskite film located on the surface of the three-dimensional perovskite film. A Cl and / or Br halide gradient extending from the defective surface and grain boundary to the bulk three-dimensional layer is formed in the three-dimensional perovskite film. The two-dimensional perovskite film is rich in iodide. The holding temperature of the second heat treatment is T2, T2 = 150 ° C, and the holding time of the second heat treatment is 60 min.

[0045] (5) Spin-coat the surface of the perovskite absorption layer obtained in step (4) with a Spiro-OMeTAD precursor solution to form a Spiro-OMeTAD hole transport layer with a thickness of 200 nm.

[0046] (6) A 60 nm thick Au electrode is evaporated on the surface of the Spiro-OMeTAD hole transport layer obtained in step (5) to obtain a perovskite solar cell.

[0047] Example 2

[0048] This embodiment is the same as embodiment 1, except that ammonium bromide is used instead of the ammonium chloride in embodiment 1.

[0049] Example 3

[0050] This embodiment is the same as Embodiment 1, except that a mixture of ammonium chloride and ammonium bromide is used instead of the ammonium chloride in Embodiment 1, and the molar ratio of ammonium chloride to ammonium bromide in this embodiment is 1:1.

[0051] Comparative Example 1

[0052] This comparative example is the same as Example 1, except that in this comparative example, t2 = 100°C.

[0053] The photoelectric conversion efficiency of the perovskite solar cells of Examples 1 to 3 and Comparative Example 1 was tested, and the test results are shown in Table 1.

[0054] Table 1. Photovoltaic conversion efficiency of perovskite solar cells of Examples 1 to 3 and Comparative Example 1

[0055]

[0056] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0057] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a stabilized perovskite absorption layer, characterized in that: The following steps are involved: S1. Preparation of perovskite wet film by one-step or two-step method; S2. performing a first heat treatment on the perovskite film to obtain a perovskite film; wherein the holding temperature of the first heat treatment is T1; S3. Prepare Cl - and / or Br - The optimized layer solution is coated on the surface of the perovskite film to form an optimized layer solution film; S4. Perform a second heat treatment on the perovskite film and the optimized layer solution film to obtain a stabilized perovskite absorption layer, wherein the stabilized perovskite absorption layer includes a three-dimensional perovskite film and a two-dimensional perovskite film, wherein the insulation temperature of the second heat treatment is T2, and T2 is greater than or equal to T1.

2. The preparation method according to claim 1, characterized in that: In step S2, T1 is 110-130°C.

3. The preparation method according to claim 1, characterized in that: In step S3, the solute in the optimization layer solution is ammonium chloride and / or ammonium bromide.

4. The preparation method according to claim 3, characterized in that: In step S3, in the optimization layer solution, the molar concentration of the ammonium chloride and / or ammonium bromide is 0.01-0.3 mol / L.

5. The preparation method according to claim 3, characterized in that: In step S3, the solvent in the optimization layer solution is a combination of isopropanol and / or chlorobenzene and N,N-dimethylformamide.

6. The preparation method according to claim 3, characterized in that: In step S3, in the optimization layer solution, the proportion of N,N-dimethylformamide is 1 to 5 wt%.

7. The preparation method according to claim 1, characterized in that: In step S4, T2 is 140-160°C.

8. The preparation method according to claim 1, characterized in that: In step S4, T2 is greater than T1.

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