Preparation method of wide-band-gap perovskite thin film with uniform initial phase and trans-perovskite solar cell

Abstract

The invention belongs to the technical field of solar cells, and particularly relates to a preparation method of a wide-band-gap perovskite thin film with a uniform initial phase and a trans-perovskite solar cell, which comprises the following steps: mixing an additive solution containing K ions with a wide-band-gap perovskite solar precursor solution, spin-coating on a substrate, and annealing to obtain the wide-band-gap perovskite thin film. According to the invention, K ions are introduced into the perovskite precursor solution as an additive, so that the initial phase separation phenomenon caused by different halogen ion nucleation rates in the crystallization process of the wide-band-gap perovskite film is optimized. The strategy not only promotes the uniform growth of crystals in the perovskite thin film, but also effectively inhibits the problems of large defect density caused by the non-uniform initial phase, halogen ion migration under an illumination condition and the like, reduces the voltage loss of the trans-perovskite solar cell under an open circuit condition, and improves the conversion efficiency of the trans-perovskite solar cell. Therefore, higher photoelectric conversion efficiency and better long-term stability are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing a wide bandgap perovskite film with uniform initial phase and an inverse perovskite solar cell. Background Art

[0002] With the rapid development of the photovoltaic industry, the efficiency of traditional single-junction solar cells has almost reached its limit, and tandem solar cells have successfully broken through this limit by stacking cell materials with different band gaps. Theoretically, the photoelectric conversion efficiency of perovskite / perovskite / crystalline silicon triple-junction tandem solar cells can reach about 51%, which is far beyond the efficiency limit of single-junction cells. Given its potential for high efficiency, silicon-based triple-junction tandem perovskite solar cells have become a hot spot in solar technology research.

[0003] To date, the photoelectric conversion efficiency (PCE) of perovskite / perovskite / crystalline silicon triple-junction tandem solar cells has exceeded 27%, which undoubtedly demonstrates its huge development potential. Even so, there is still a large gap between its actual performance and the theoretical maximum efficiency, which means that there are still many technical problems to be overcome in the process of commercializing these cells. In particular, wide-bandgap perovskite solar cells, which are the core components of triple-junction tandem solar cells, have achieved certain results in material design and photoelectric performance improvement, but still face a series of problems such as large open-circuit voltage loss and poor wet / thermal stability. Specifically, due to the bromine (Br)-rich organic-inorganic hybrid wide-bandgap perovskite, phase separation will occur under continuous illumination, thereby forming a narrow-bandgap iodine (I)-rich phase and a wide-bandgap Br-rich phase. This light-induced phase separation will cause the carriers to rapidly thermalize and accumulate in the I-rich region, which is one of the main reasons for the reduction in device performance.

[0004] Traditional methods to suppress phase separation mainly use strategies such as relaxing residual strain or adding low-dimensional perovskites to delay phase segregation by inhibiting ion migration. And studies have found that local ion aggregation caused by initial film inhomogeneity is one of the main reasons for the occurrence of phase segregation. Optimizing the initial phase separation of wide-bandgap perovskite solar cells is an important factor in obtaining wide-bandgap perovskite solar cells with both high stability and high performance. Summary of the invention

[0005] In view of this, the present invention proposes a method for preparing a wide bandgap perovskite film with uniform initial phase and an inverse perovskite solar cell, by doping potassium ions in a spin coating precursor solution, the initial phase separation phenomenon caused by different halogen ion nucleation rates during the crystallization process of the wide bandgap perovskite film is optimized, and a perovskite film with uniform initial film and good crystallization quality is obtained.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing a wide bandgap perovskite film with uniform initial phase, comprising the following steps:

[0008] Step 1: Prepare wide bandgap perovskite precursor solution:

[0009] Dissolving CsI, MAI, FAI, PbBr2 and PbCl2 in a mixed solvent at a molar ratio of 0.1:0.1:0.8:0.9:0.1, and stirring to obtain a wide bandgap perovskite precursor solution;

[0010] Dissolving KX in dimethyl sulfoxide (DMSO) at a molar concentration of less than 1 mol / L and greater than 0.1 mol / L, and stirring to obtain an additive solution;

[0011] Step 2, adding the prepared additive solution to the wide band gap perovskite precursor solution to obtain an optimized wide band gap perovskite precursor solution;

[0012] Step 3: Spin the optimized wide bandgap perovskite precursor solution onto the substrate layer by a spin coater, and anneal to obtain an initially uniform wide bandgap perovskite film. The crystal structure of the initially uniform wide bandgap perovskite film is ABX3, wherein the A-site cation includes MA + , FA + , Cs + , Rb + and its mixed system, the metal ions at the B site include Pb 2+ , X-position halogen ions include I - Br - , Cl - , halogen-like elements with similar ionic radius and their mixed systems, the band gap ranges from 1.8eV to 2.1eV.

[0013] Furthermore, in the step 1, X in KX used to prepare the additive solution is a halogen ion, including I - Br - , Cl - , halogen-like elements with similar ionic radius and their mixed systems.

[0014] Furthermore, the mixed solvent in step 1 is composed of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and the volume ratio of DMF to DMSO is 4:1.

[0015] Furthermore, in the step 2, in the optimized wide bandgap perovskite precursor solution, the molar concentration of the additive solution added in the precursor solution is less than 1% mol / L but not 0 mol / L. Furthermore, in the step 3, the process of spin coating on the substrate material is divided into two stages, specifically:

[0016] The speed of the spin coater in the first stage was 1000-2000 rpm, the duration was 1000 s, and the speed of the second stage was 4000-5000 rpm, the duration was 40 s;

[0017] At 20-25 seconds after the start of the second stage, 0.1-0.2 mL of chlorobenzene antisolvent was dripped onto the rotating substrate surface;

[0018] After the second stage of spin coating, the obtained product is placed on a hot stage and annealed at a temperature range of 100 to 120° C. for 10 to 15 minutes to obtain an initial phase-uniform wide bandgap perovskite film.

[0019] A method for preparing an inverted perovskite solar cell, wherein the device structure of the inverted perovskite solar cell is as follows from bottom to top: the device structure of the wide bandgap perovskite solar cell is as follows from bottom to top: an ITO conductive substrate layer, a hole transport layer, a wide bandgap perovskite light absorbing layer, an electron transport layer, and a metal electrode layer, specifically comprising the following steps:

[0020] (1) Preparing a hole transport layer on the ITO conductive substrate layer;

[0021] (2) using the preparation method described in any one of claims 1 to 5 to prepare a wide bandgap perovskite film on the hole transport layer as a wide bandgap perovskite light absorbing layer;

[0022] (3) An electron transport layer and a metal electrode layer are sequentially prepared on the wide bandgap perovskite light absorbing layer to obtain an inverse perovskite solar cell.

[0023] The preparation method of the wide band gap perovskite film and the inverse perovskite solar cell of the present invention suppresses the initial phase separation phenomenon of the wide band gap perovskite solar cell by introducing an additive solution, thereby improving the film quality of the wide band gap perovskite. Specifically: the K ions in the additive solution are between the Rb ions and the Na ions in terms of their ion radius, so that the K ions can enter the perovskite lattice gap position. During the crystallization process of the perovskite film, the local ion aggregation phenomenon during the crystallization of the wide band gap perovskite film is suppressed by blocking the preferred path of ion migration. At the same time, the K ions can promote the uniform growth of crystals and improve the crystallinity of the film during the film formation process. This improved crystal quality helps to delay the phase segregation phenomenon of the wide band gap perovskite under illumination conditions, reduce the defect state in the film, reduce non-radiative recombination, and effectively improve the film quality of the wide band gap perovskite. When it is applied to the inverse perovskite solar cell, it can reduce the open circuit voltage loss of the inverse perovskite solar cell, and obtain a higher photoelectric conversion efficiency (PCE) and better long-term stability.

[0024] Compared with the prior art, the present invention can at least achieve the following beneficial effects:

[0025] 1. The present invention optimizes the initial phase separation phenomenon of the wide-bandgap perovskite film by introducing additive solvents to regulate the crystallization process, thereby improving the crystallization quality of the perovskite and significantly inhibiting the occurrence of phase segregation under light conditions, thereby laying a solid material foundation for the manufacture of high-performance perovskite solar cells.

[0026] 2. In inverted perovskite solar cells, the wide-bandgap perovskite film prepared by the present invention can effectively reduce its open-circuit voltage loss during operation, promote a significant improvement in the photoelectric conversion efficiency, and provide a new technical path for achieving more efficient solar energy utilization.

[0027] 3. The wide-bandgap perovskite film preparation method of the present invention can be used to manufacture the wide-bandgap perovskite light-absorbing layer of the perovskite / perovskite / silicon triple-junction stacked solar cell. This integration strategy is conducive to optimizing cell performance and opens up a new direction for improving the photoelectric conversion efficiency of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the solar cell structure of the embodiment and the comparative example.

[0029] Figure 2 PL Mapping diagrams of the wide bandgap perovskite films of the embodiments and comparative examples; wherein: (a) is the PL mapping diagram of the comparative example, (b) is the PL mapping diagram of embodiment 1, (c) is the PL mapping diagram of embodiment 2, and (d) is the PL mapping diagram of embodiment 3.

[0030] Figure 3 The figures are the morphologies of the wide bandgap perovskite film surfaces of the embodiments and the comparative examples under a scanning electron microscope (SEM); (a) is the morphology of the wide bandgap perovskite film surface of the comparative example under a scanning electron microscope (SEM); (b) is the morphology of the wide bandgap perovskite film surface of Example 1 under a scanning electron microscope (SEM); (c) is the morphology of the wide bandgap perovskite film surface of Example 2 under a scanning electron microscope (SEM); (d) is the morphology of the wide bandgap perovskite film surface of Example 3 under a scanning electron microscope (SEM).

[0031] Figure 4 X-ray diffraction (XRD) patterns of the wide bandgap perovskite films of the embodiments and comparative examples.

[0032] Figure 5 The current density-voltage (JV) curves of the inverse perovskite solar cells obtained in the examples and comparative examples are shown. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the examples and the accompanying drawings. Where specific experimental steps or conditions are not specified in the examples, the conventional experimental steps or conditions described in the literature in the art can be used. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional reagent products that can be purchased.

[0034] Example 1

[0035] This embodiment provides a method for preparing a wide bandgap perovskite film with an initial uniform phase, comprising the following steps:

[0036] Step A1: Preparation of wide bandgap perovskite precursor solution and additive solution:

[0037] Prepare a wide bandgap perovskite precursor solution: weigh 26.0 mg of CsI, 15.9 mg of MAI, 137.6 mg of FAI, 330.3 mg of PbBr2, and 27.8 mg of PbCl2, dissolve them in 1 mL of a mixed solvent and stir for 12 hours. The mixed solvent consists of DMF and DMSO in a volume ratio of DMF to DMSO of 4:1, thereby obtaining a wide bandgap perovskite precursor solution.

[0038] Preparation of additive solution: 16.5 mg of RbBr was weighed and dissolved in 1 mL of DMSO solvent and stirred to obtain an additive solution.

[0039] Step A2: preparing an optimized wide bandgap perovskite precursor solution: taking 0.05 mL of the additive solution obtained in step 3.2 and adding it to the wide bandgap perovskite precursor solution obtained in step 3.1, thereby obtaining an optimized wide bandgap perovskite precursor solution.

[0040] Step A3: Spin coating perovskite film: The optimized wide bandgap perovskite precursor solution is spin coated on the substrate layer by a spin coater. The rotation speed of the spin coater is divided into two stages. The rotation speed of the first stage is 1000 rpm and the duration is 10 s. The rotation speed of the second stage is 4000 rpm and the duration is 40 s. At 25 s in the second stage, 0.15 mL of chlorobenzene antisolvent is dropped onto the rotating substrate surface.

[0041] Step A4, film annealing: the spin-coated sample is placed on a hot stage and annealed at 100° C. for 10 min to obtain a wide bandgap perovskite film.

[0042] Based on the wide bandgap perovskite film prepared by the above method, this embodiment further provides an inverted perovskite solar cell, and the preparation method of the inverted perovskite solar cell comprises:

[0043] Step 1: Clean the substrate:

[0044] In this embodiment, indium tin oxide (ITO) glass is selected as the substrate; first, deionized water, acetone, and anhydrous ethanol are used for ultrasonic cleaning for 15 minutes each, the washed substrate is blown dry with a nitrogen gun and stored in a dry environment, and treated with a UV-ozone cleaning device for 30 minutes before use.

[0045] Step 2: Preparation of hole transport layer:

[0046] In this embodiment, a composite structure of nickel oxide (NiOx) and [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphoric acid (Me-4PACz) is used as the hole transport layer, and the preparation steps are as follows:

[0047] Step 2.1: Weigh a certain amount of NiOx nanoparticles and dissolve them in deionized water to prepare a NiOx nanodispersed solution with a concentration of 10 mg / mL.

[0048] Step 2.2: Spin the NiOx solution onto the ITO substrate using a spin coater at a speed of 4000 rpm for 30 s, and then anneal on a hot stage at 100°C for 10 min.

[0049] Step 2.3: Weigh a certain amount of Me-4PACz and dissolve it in anhydrous ethanol to prepare a Me-4PACz solution with a concentration of 1 mg / mL.

[0050] Step 2.4: Spin the Me-4PACz solution onto the NiOx surface using a spin coater at a spin coating speed of 3000 rpm for 30 seconds, and then anneal on a hot stage at 100° C. for 10 minutes to obtain a hole transport layer.

[0051] Step 3: According to the above steps A1-A4, a wide bandgap perovskite thin film layer is prepared on the hole transport layer.

[0052] Step 4: Preparation of electron transport layer:

[0053] In this embodiment, a composite structure of [6,6]-phenyl-C61-butyric acid isomethyl ester (PCBM) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) is selected as the electron transport layer, and the preparation steps are as follows:

[0054] Step 4.1: Weigh a certain amount of PCBM and dissolve it in chlorobenzene (CB) to prepare a PCBM solution with a concentration of 15 mg / mL.

[0055] Step 4.2: Spin coat the PCBM solution onto the surface of the wide bandgap perovskite film using a spin coater at a spin coating speed of 1500 rpm for 30 seconds, followed by annealing at 100°C on a hot stage for 5 minutes.

[0056] Step 4.3: Weigh a certain amount of BCP and dissolve it in isopropanol (IPA) to prepare a BCP solution with a concentration of 2 mg / mL.

[0057] Step 4.4: Spin the BCP solution onto the PCBM surface using a spin coater at a spin coating speed of 5000 rpm for 20 seconds, and then anneal on a hot stage at 80° C. for 1 minute. Thus, an electron transport layer is obtained.

[0058] Step 5: Preparation of metal electrodes:

[0059] In this embodiment, silver is selected as the metal electrode, and the preparation method is: 120nm of silver is deposited on the surface of the electron transport layer by vacuum thermal evaporation through a mask. Figure 1 The complete inverse perovskite solar cell shown.

[0060] Example 2

[0061] The preparation method of the initially phase-uniform wide bandgap perovskite film and the preparation method of the inverse perovskite solar cell provided in this embodiment have preparation steps that are basically the same as those in Example 1, with the only difference being that the additive solution used in the preparation stage of the wide bandgap perovskite film layer in Example 2 is a KBr solution.

[0062] Example 3

[0063] The preparation method of the initially phase-uniform wide bandgap perovskite film and the inverse perovskite solar cell provided in this embodiment has the same preparation steps as those in Example 1, except that the additive solution used in the preparation stage of the wide bandgap perovskite layer in Example 3 is a NaBr solution.

[0064] Comparative Example

[0065] This comparative example provides a method for preparing a wide bandgap perovskite film and an inverse perovskite solar cell with an initial uniform phase. The preparation steps are basically the same as those in Example 1, except that: in the comparative example, no additive solution is added to the wide bandgap perovskite precursor solution during the preparation stage of the wide bandgap perovskite film layer, but the obtained wide bandgap perovskite precursor solution is directly spin-coated on the substrate / hole transport layer by a spin coater.

[0066] The above embodiments and comparative examples are analyzed and tested below:

[0067] The wide bandgap perovskite films obtained in the examples and comparative examples were subjected to PL Mapping tests, and the results are as follows: Figure 2 As shown, Figure 2 (a) corresponding to the film obtained in the corresponding proportion, Figure 2 (b) corresponds to the film obtained in Example 1, Figure 2 (c) corresponds to the film obtained in Example 2, Figure 2 (d) The film obtained in the corresponding embodiment 3. From the PL Mapping image, it can be seen that the fluorescence response distribution of the comparative sample is uneven, wherein the high fluorescence response area corresponds to the I-rich phase area, and the low fluorescence response area corresponds to the Br-rich phase area. It can be seen that after the addition of alkali metal ions, the fluorescence response distribution of each embodiment is improved, among which the fluorescence response distribution of embodiment 2 is the most uniform, indicating that the addition of K ions can inhibit the local aggregation of halogen ions.

[0068] The wide bandgap perovskite films obtained in the examples and comparative examples were subjected to PL Mapping tests, and the results are as follows: Figure 2 As shown, Figure 2 (a) corresponding to the film obtained in the corresponding proportion, Figure 2 (b) corresponds to the film obtained in Example 1, Figure 2 (c) corresponds to the film obtained in Example 2, Figure 2 (d) The film obtained in the corresponding embodiment 3. From the PL Mapping image, it can be seen that the fluorescence response distribution of the comparative sample is uneven, wherein the high fluorescence response area corresponds to the I-rich phase area, and the low fluorescence response area corresponds to the Br-rich phase area. It can be seen that after the addition of alkali metal ions, the fluorescence response distribution of each embodiment is improved, among which the fluorescence response distribution of embodiment 2 is the most uniform, indicating that the addition of K ions can inhibit the local aggregation of halogen ions.

[0069] The wide bandgap perovskite films obtained in the examples and comparative examples were subjected to SEM analysis, and the results are as follows: Figure 3 As shown, Figure 3 (a) corresponding to the film obtained in the corresponding proportion, Figure 3 (b) corresponds to the film obtained in Example 1, Figure 3(c) corresponds to the film obtained in Example 2, Figure 3 (d) The film obtained in the corresponding embodiment 3. From the SEM image, it can be seen that a large number of strip-shaped areas appear on the surface of the comparative sample, which are I-rich phase areas, while the flat areas are Br-rich phase areas, indicating that the comparative example has a serious phase separation phenomenon. After adding additives, the surface morphology of the embodiments has undergone different changes, among which the surface morphology of embodiment 2 is smoother than that of the comparative example and other embodiments, indicating that its phase separation phenomenon is significantly suppressed.

[0070] XRD analysis was performed on the wide bandgap perovskite films obtained in the examples and comparative examples. The results are as follows: Figure 4 As shown in the figure, compared with the comparative example, after the introduction of K ions, the characteristic peak (corresponding to a 2θ value of 14.6°) of the perovskite in Example 2 has a certain increase in intensity, reflecting the good crystallinity of the perovskite, indicating its good crystal quality. The photovoltaic test of the inverse perovskite solar cells obtained in the examples and comparative examples shows that the effective active area is 0.053 cm 2 The test conditions are standard simulated sunlight AM1.5 and temperature 25°C. The JV curves of the embodiment and the comparative example are shown in FIG. Figure 5 Compared with the comparative example, Example 2 has obvious improvements in open circuit voltage, current density and fill factor, and the energy conversion efficiency is also improved by 1.6%, which shows that the photovoltaic performance of the solar cell device is optimized under the action of the additive solution of the wide bandgap perovskite film.

[0071] Table 1: Comparison of photovoltaic parameters of inverse perovskite solar cells obtained in the examples and comparative examples

[0072]

[0073] As can be seen from Table 1, the preparation method of this embodiment, by introducing K ions as additives into the perovskite precursor solution, optimizes the initial phase separation phenomenon caused by different halogen ion nucleation rates during the crystallization of the wide-bandgap perovskite film, promotes the uniform growth of crystals in the perovskite film, and effectively suppresses the high defect density caused by the initial phase inhomogeneity and the halogen ion migration under light conditions.

[0074] The above embodiments are intended to provide a better understanding of the present invention, but are not limited to the optimal implementation mode and do not constitute a limitation on the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts shall be within the protection scope of the present invention.

Claims

1. A method for preparing a wide bandgap perovskite film with uniform initial phase, characterized in that: The following steps are involved: Step 1: Prepare wide bandgap perovskite precursor solution: Dissolving CsI, MAI, FAI, PbBr2 and PbCl2 in a mixed solvent at a molar ratio of 0.1:0.1:0.8:0.9:0.1, and stirring to obtain a wide bandgap perovskite precursor solution; Dissolving KX in dimethyl sulfoxide (DMSO) at a molar concentration of less than 1 mol / L and greater than 0.1 mol / L, and stirring to obtain an additive solution; Step 2, adding the prepared additive solution to the wide band gap perovskite precursor solution to obtain an optimized wide band gap perovskite precursor solution; Step 3: The optimized wide bandgap perovskite precursor solution is spin-coated on the substrate layer by a spin coater, and then annealed to obtain an initial phase-uniform wide bandgap perovskite film.

2. The preparation method according to claim 1, characterized in that: In the step 1, X in KX used to prepare the additive solution is a halogen ion, including I - Br - , Cl - , halogen-like elements with similar ionic radius and their mixed systems.

3. The preparation method according to claim 2, characterized in that: The mixed solvent in step 1 is composed of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and the volume ratio of DMF to DMSO is 4:

1.

4. The preparation method according to claim 3, characterized in that: In the step 2, the molar concentration of the additive solution added to the optimized wide bandgap perovskite precursor solution is less than 1% mol / L but not 0 mol / L.

5. The preparation method according to claim 4, characterized in that: The process of spin coating on the substrate material in step 3 is divided into two stages, specifically: The speed of the spin coater in the first stage was 1000-2000 rpm, the duration was 1000 s, and the speed of the second stage was 4000-5000 rpm, the duration was 40 s; At 20-25 seconds after the start of the second stage, 0.1-0.2 mL of chlorobenzene antisolvent was dripped onto the rotating substrate surface; After the second stage of spin coating, the obtained product is placed on a hot stage and annealed at a temperature range of 100 to 120° C. for 10 to 15 minutes to obtain an initial phase-uniform wide bandgap perovskite film.

6. An initially phase-uniform wide bandgap perovskite film, characterized in that: The film is prepared by the method for preparing a wide bandgap perovskite film with uniform initial phase as described in any one of claims 1 to 5.

7. A method for preparing an inverse perovskite solar cell, characterized in that: The device structure of the inverted perovskite solar cell is as follows from bottom to top: The device structure of the wide bandgap perovskite solar cell is as follows from bottom to top: an ITO conductive substrate layer, a hole transport layer, a wide bandgap perovskite light absorbing layer, an electron transport layer, and a metal electrode layer, specifically comprising the following steps: (1) Preparing a hole transport layer on the ITO conductive substrate layer; (2) using the preparation method described in any one of claims 1 to 5 to prepare a wide bandgap perovskite film on the hole transport layer as a wide bandgap perovskite light absorbing layer; (3) An electron transport layer and a metal electrode layer are sequentially prepared on the wide bandgap perovskite light absorbing layer to obtain an inverse perovskite solar cell.

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