A method for preparing a wide-bandgap perovskite thin film with uniform initial phase and an inverted perovskite solar cell.

Abstract

This invention belongs to the field of solar cell technology, specifically a method for preparing a wide-bandgap perovskite thin film with a uniform initial phase and an inverted perovskite solar cell. The method involves mixing a K-ion-containing additive solution with a wide-bandgap perovskite solar cell precursor solution, spin-coating the mixture onto a substrate, and annealing to obtain the wide-bandgap perovskite thin film. This invention optimizes the initial phase separation phenomenon caused by different halide ion nucleation rates during the crystallization process of the wide-bandgap perovskite thin film by introducing K-ions as an additive into the perovskite precursor solution. This strategy not only promotes uniform crystal growth in the perovskite thin film but also effectively suppresses problems such as high defect density caused by initial phase inhomogeneity and halide ion migration under illumination, reducing voltage loss of the inverted perovskite solar cell under open-circuit conditions, thereby achieving higher photoelectric conversion efficiency and better long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a method for preparing a wide-bandgap perovskite thin film with uniform initial phase and an inverted perovskite solar cell. Background Technology

[0002] With the rapid development of the photovoltaic industry, the efficiency of traditional single-junction solar cells has almost reached its limit. Tandem solar cells, by stacking cell materials with different band gaps, have successfully overcome this limitation. Theoretically, the photoelectric conversion efficiency of perovskite / perovskite / crystalline silicon triple-junction tandem solar cells can reach approximately 51%, a figure far exceeding the efficiency limit of single-junction cells. Given its high efficiency potential, silicon-based triple-junction tandem perovskite solar cells have become a hot topic in solar energy technology research.

[0003] To date, the photoelectric conversion efficiency (PCE) of perovskite / perovskite / crystalline silicon triple-junction tandem solar cells has exceeded 27%, undoubtedly demonstrating their enormous development potential. Even so, their actual performance still falls significantly short of the theoretical maximum efficiency, meaning that many technical challenges remain to be overcome in the commercialization of these cells. In particular, wide-bandgap perovskite solar cells, as the core component of triple-junction tandem solar cells, despite some progress in material design and photoelectric performance improvement, still face a series of problems such as high open-circuit voltage loss and poor humidity / thermal stability. Specifically, under continuous illumination, bromine (Br)-rich organic-inorganic hybrid wide-bandgap perovskite undergoes phase separation, forming a narrow-bandgap iodine (I)-rich phase and a wide-bandgap Br-rich phase. This light-induced phase separation causes carriers to rapidly heat up and accumulate in the I-rich region, which is one of the main reasons for the degraded device performance.

[0004] Traditional methods for suppressing phase separation mainly employ strategies such as relaxing residual strain or adding low-dimensional perovskites to delay phase segregation by inhibiting ion migration. Furthermore, research has found that localized ion aggregation caused by initial film inhomogeneity is one of the main causes of phase segregation. Optimizing the initial phase separation of wide-bandgap perovskite solar cells is a crucial factor in obtaining wide-bandgap perovskite solar cells that possess 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 thin film with uniform initial phase and an inverted perovskite solar cell. By doping potassium ions in the spin-coating precursor solution, the initial phase separation phenomenon caused by different nucleation rates of halide ions during the crystallization process of the wide-bandgap perovskite thin film is optimized, thereby obtaining a perovskite thin film with uniform initial phase and good crystal quality.

[0006] The technical solution adopted in this invention is as follows:

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

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

[0009] CsI, MAI, FAI, PbBr2 and PbCl2 were dissolved in a mixed solvent in a molar ratio of 0.1:0.1:0.8:0.9:0.1 and stirred to obtain a wide-bandgap perovskite precursor solution.

[0010] KX was dissolved in dimethyl sulfoxide (DMSO) at a molar concentration of less than 1 mol / L and greater than 0.1 mol / L, and the mixture was stirred to obtain an additive solution.

[0011] Step 2: Add the prepared additive solution to the wide-bandgap perovskite precursor solution to obtain the optimized wide-bandgap perovskite precursor solution.

[0012] Step 3: The optimized wide-bandgap perovskite precursor solution was spin-coated onto the substrate using a spin coater. After annealing, a wide-bandgap perovskite film with a uniform initial phase was obtained. The crystal structure of this wide-bandgap perovskite film with a uniform initial phase is ABX3, wherein the A-site cations include MA. + FA + Cs + 、Rb + and its mixed systems, with B-site metal ions including Pb 2+ The X-position halide ion includes I - ,Br - Cl - Halogen-like substances and their mixtures with similar ionic radii have band gaps ranging from 1.8 eV to 2.1 eV.

[0013] Furthermore, in step 1, the X in KX used to prepare the additive solution is a halide ion, including I... - ,Br - Cl - Halogens with similar ionic radii 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 step 2, the additive solution added to the optimized wide-bandgap perovskite precursor solution has a molar concentration of less than 1% mol / L but not 0 mol / L in the precursor solution. Furthermore, in step 3, the spin-coating process on the substrate material is divided into two stages, specifically:

[0016] The first stage of the spin coater has a rotation speed of 1000-2000 rpm and a duration of 1000 s; the second stage has a rotation speed of 4000-5000 rpm and a duration of 40 s.

[0017] At the beginning of the second stage, 0.1-0.2 mL of chlorobenzene antisolvent is dropped onto the rotating substrate surface at 20-25 seconds.

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

[0019] A method for fabricating an inverted perovskite solar cell, wherein the device structure of the inverted perovskite solar cell, from bottom to top, comprises: 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 including the following steps:

[0020] (1) A hole transport layer is prepared on an ITO conductive substrate;

[0021] (2) A wide-bandgap perovskite thin film is prepared on the hole transport layer by the preparation method described in any one of claims 1 to 5, so as to serve 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 inverted perovskite solar cell.

[0023] The present invention discloses a method for preparing wide-bandgap perovskite thin films and inverted perovskite solar cells. By introducing an additive solution, the initial phase separation phenomenon in wide-bandgap perovskite solar cells is suppressed, thereby improving the film quality. Specifically, the K ions in the additive solution, due to their ionic radius being between that of Rb and Na ions, can enter the interstitial positions of the perovskite lattice. During the crystallization process of the perovskite film, by blocking the preferred ion migration path, local ion aggregation during the crystallization of the wide-bandgap perovskite film is suppressed. Simultaneously, K ions can promote uniform crystal growth and improve the crystallinity of the film during film formation. This improved crystal quality helps to delay phase segregation in wide-bandgap perovskite under illumination, reduces defect states in the film, and decreases non-radiative recombination, effectively improving the film quality of wide-bandgap perovskite. When applied to inverted perovskite solar cells, it can reduce the open-circuit voltage loss of the inverted perovskite solar cells, resulting in higher photoelectric conversion efficiency (PCE) and better long-term stability.

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

[0025] 1. This invention optimizes the initial phase separation phenomenon of wide-bandgap perovskite films by introducing additive solvents to regulate the crystallization process, thereby improving the crystallization quality of perovskite and significantly suppressing phase segregation under illumination, thus 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 thin film prepared by this invention can effectively reduce the open-circuit voltage loss during operation, significantly improve the photoelectric conversion efficiency, and provide a new technical path for achieving more efficient solar energy utilization.

[0027] 3. The wide-bandgap perovskite thin film preparation method of the present invention can be used to manufacture the wide-bandgap perovskite light-absorbing layer of perovskite / perovskite / silicon triple junction tandem solar cells. This integration strategy is beneficial to optimizing cell performance and opens up a new direction for improving the photoelectric conversion efficiency of solar cells. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the solar cell structure for both the embodiment and the comparative example.

[0029] Figure 2 The following are photoluminescence spectra (PL mappings) of wide-bandgap perovskite thin films in the examples and comparative examples; wherein: (a) is the photoluminescence spectrum of the comparative example, (b) is the photoluminescence spectrum of Example 1, (c) is the photoluminescence spectrum of Example 2, and (d) is the photoluminescence spectrum of Example 3.

[0030] Figure 3 The images show the surface morphology of the wide-bandgap perovskite films in the examples and comparative examples under a scanning electron microscope (SEM); (a) is the surface morphology of the wide-bandgap perovskite film in the comparative example under a scanning electron microscope (SEM); (b) is the surface morphology of the wide-bandgap perovskite film in Example 1 under a scanning electron microscope (SEM); (c) is the surface morphology of the wide-bandgap perovskite film in Example 2 under a scanning electron microscope (SEM); and (d) is the surface morphology of the wide-bandgap perovskite film in Example 3 under a scanning electron microscope (SEM).

[0031] Figure 4 The X-ray diffraction (XRD) patterns of the wide-bandgap perovskite thin films used in the examples and comparative examples are shown.

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

[0033] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all conventional reagent products that can be purchased.

[0034] Example 1

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

[0036] Step A1: Prepare wide-bandgap perovskite precursor solution and additive solution:

[0037] Preparation of 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 and dissolve them in 1 mL of a mixed solvent and stir for 12 h. The mixed solvent consists of DMF and DMSO with a volume ratio of DMF to DMSO of 4:1. This yields the wide-bandgap perovskite precursor solution.

[0038] Preparation of additive solution: Weigh 16.5 mg of RbBr and dissolve it in 1 mL of DMSO solvent and stir to obtain the additive solution.

[0039] Step A2: Prepare the optimized wide-bandgap perovskite precursor solution: Take 0.05 mL of the additive solution obtained in step 3.2 and add it to the wide-bandgap perovskite precursor solution obtained in step 3.1 to obtain the optimized wide-bandgap perovskite precursor solution.

[0040] Step A3: Spin-coating perovskite film: The optimized wide-bandgap perovskite precursor solution was spin-coated onto the substrate using a spin coater. The spin coater speed was divided into two stages: the first stage was at 1000 rpm for 10 seconds, and the second stage was at 4000 rpm for 40 seconds. At the 25th second of the second stage, 0.15 mL of chlorobenzene antisolvent was dropped onto the rotating substrate surface.

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

[0042] Based on the wide-bandgap perovskite thin film prepared by the above method, this embodiment also provides an inverted perovskite solar cell, the preparation method of which includes:

[0043] Step 1: Clean the substrate:

[0044] In this embodiment, indium tin oxide (ITO) glass is used as the substrate. First, the substrate is ultrasonically cleaned for 15 minutes each with deionized water, acetone, and anhydrous ethanol. The cleaned substrate is dried with a nitrogen gun and stored in a dry environment. Before use, it is treated with an ultraviolet-ozone cleaning device for 30 minutes.

[0045] Step 2: Prepare the hole transport layer:

[0046] In this embodiment, a composite structure of nickel oxide (NiOx) and [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphate (Me-4PACz) is selected as the hole transport layer. 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 nanoparticle dispersion solution with a concentration of 10 mg / mL.

[0048] Step 2.2: Spin coat the NiOx solution onto the ITO substrate using a spin coater at a speed of 4000 rpm for 30 s, and then anneal it on a hot plate 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: The Me-4PACz solution was spin-coated onto the NiOx surface using a spin coater at 3000 rpm for 30 seconds, followed by annealing at 100°C for 10 minutes on a hot plate. This yielded the hole transport layer.

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

[0052] Step 4: Fabrication of the electron transport layer:

[0053] In this embodiment, a composite structure of [6,6]-phenyl-C61-butyrate isomethyl ester (PCBM) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was selected as the electron transport layer. 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 speed of 1500 rpm for 30 s, and then anneal it on a hot plate at 100 °C for 5 min.

[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 coat the BCP solution onto the PCBM surface using a spin coater at 5000 rpm for 20 seconds, then anneal at 80°C for 1 minute on a hot plate. This yields the electron transport layer.

[0058] Step 5: Prepare the metal electrode:

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

[0060] Example 2

[0061] The preparation methods for the wide-bandgap perovskite thin film with uniform initial phase and the preparation methods for the inverted perovskite solar cell provided in this embodiment are basically the same as those in Example 1. The only difference is that the additive solution used in the preparation stage of the wide-bandgap perovskite thin film layer in Example 2 is KBr solution.

[0062] Example 3

[0063] The preparation steps of the wide-bandgap perovskite thin film with uniform initial phase and the inverted perovskite solar cell provided in this embodiment are basically the same as those in Example 1. The only difference is that the additive solution used in the preparation stage of the wide-bandgap perovskite layer in Example 3 is NaBr solution.

[0064] Comparative Example

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

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

[0067] PL mapping tests were performed on the wide-bandgap perovskite films obtained in the examples and comparative examples, and the results are as follows: Figure 2 As shown, where Figure 2 (a) The corresponding film obtained in proportion, Figure 2 (b) The film obtained in Example 1, Figure 2 (c) The film obtained in Example 2, Figure 2 (d) The film obtained in Example 3. The PL mapping image shows that the fluorescence response distribution of the comparative sample is uneven, with high fluorescence response areas corresponding to I-rich phase regions and low fluorescence response areas corresponding to Br-rich phase regions. It can be seen that the fluorescence response distribution of each example is improved after the addition of alkali metal ions, with Example 2 showing the most uniform fluorescence response distribution, indicating that the addition of K ions can suppress the local aggregation of halide ions.

[0068] PL mapping tests were performed on the wide-bandgap perovskite films obtained in the examples and comparative examples, and the results are as follows: Figure 2 As shown, where Figure 2 (a) The corresponding film obtained in proportion, Figure 2 (b) The film obtained in Example 1, Figure 2 (c) The film obtained in Example 2, Figure 2 (d) The film obtained in Example 3. The PL mapping image shows that the fluorescence response distribution of the comparative sample is uneven, with high fluorescence response areas corresponding to I-rich phase regions and low fluorescence response areas corresponding to Br-rich phase regions. It can be seen that the fluorescence response distribution of each example is improved after the addition of alkali metal ions, with Example 2 showing the most uniform fluorescence response distribution, indicating that the addition of K ions can suppress the local aggregation of halide ions.

[0069] SEM analysis was performed on the wide-bandgap perovskite films obtained in the examples and comparative examples, and the results are as follows: Figure 3 As shown, where Figure 3 (a) The corresponding film obtained in proportion, Figure 3 (b) The film obtained in Example 1, Figure 3(c) The film obtained in Example 2, Figure 3 (d) The film obtained in Example 3. SEM images show that the comparative sample exhibits numerous strip-shaped regions on its surface, which are I-rich regions, while the flat regions are Br-rich regions, indicating severe phase separation in the comparative sample. After the addition of additives, the surface morphology of all examples changed differently. The surface morphology of Example 2 was smoother than that of the comparative and other examples, indicating that phase separation was significantly suppressed.

[0070] XRD analysis was performed on the wide-bandgap perovskite films obtained in the examples and comparative examples, and the results are as follows: Figure 4 As shown, compared to the comparative example, the intensity of the characteristic peak (corresponding to a 2θ value of 14.6°) of the perovskite in Example 2 increased after the introduction of K ions, indicating better crystallinity and thus good crystal quality. Photovoltaic tests were conducted on the inverse perovskite solar cells obtained in both examples and the comparative example, and the effective active area was 0.053 cm². 2 The test conditions were standard simulated sunlight AM1.5 and a temperature of 25°C. The JV curves for the example and comparative examples are shown below. Figure 5 As shown, compared to the comparative example, Example 2 shows significant improvements in open-circuit voltage, current density, and fill factor, and the energy conversion efficiency is also improved by 1.6%. This indicates that the photovoltaic performance of the solar cell device is optimized by the addition of the additive solution to the wide-bandgap perovskite thin film.

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

[0072]

[0073] As shown in Table 1, the preparation method of this embodiment, by introducing K ions as an additive into the perovskite precursor solution, optimizes the initial phase separation phenomenon caused by the different nucleation rates of halide ions during the crystallization process of wide-bandgap perovskite films, promotes the uniform growth of crystals in perovskite films, and effectively suppresses problems such as high defect density caused by initial phase inhomogeneity and halide ion migration under illumination.

[0074] The above embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, is within the scope of protection of the present invention.

Claims

1. A method for preparing a wide-bandgap perovskite thin film with a uniform initial phase, characterized in that, Includes the following steps: Step 1: Prepare a wide-bandgap perovskite precursor solution: CsI, MAI, FAI, PbBr2 and PbCl2 were dissolved in a mixed solvent in a molar ratio of 0.1:0.1:0.8:0.9:0.1 and stirred to obtain a wide-bandgap perovskite precursor solution. The mixed solvent consisted of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:

1. KX was dissolved in dimethyl sulfoxide (DMSO) at a molar concentration of less than 1 mol / L and greater than 0.1 mol / L, and the solution was stirred to obtain an additive solution; the X in KX used to prepare the additive solution is a halide ion, including I... - ,Br - Cl - Halogens with similar ionic radii and their mixed systems; Step 2: Add the prepared additive solution to the wide-bandgap perovskite precursor solution to obtain the optimized wide-bandgap perovskite precursor solution; the molar concentration of the added additive solution in the precursor solution is less than 1% mol / L but not 0 mol / L; Step 3: The optimized wide-bandgap perovskite precursor solution is spin-coated onto the substrate using a spin coater, followed by annealing to obtain a wide-bandgap perovskite thin film with a uniform initial phase. The spin-coating process on the substrate material is divided into two stages, specifically: The first stage spin coater rotates at 1000-2000 rpm for 1000 seconds, and the second stage spin coater rotates at 4000-5000 rpm for 40 seconds. At the beginning of the second stage, 0.1 to 0.2 mL of chlorobenzene antisolvent is dropped onto the rotating substrate surface at 20 to 25 seconds. After the second stage of spin coating is completed, the obtained product is placed on a hot plate and annealed at a temperature range of 100~120℃ for 10~15min to obtain a wide-bandgap perovskite film with a uniform initial phase.

2. A wide-bandgap perovskite thin film with a uniform initial phase, characterized in that, The perovskite film with uniform initial phase and wide bandgap as described in claim 1 was prepared.

3. A method for preparing an inverted perovskite solar cell, characterized in that, The device structure of the inverted perovskite solar cell, from bottom to top, is as follows: The device structure of the wide-bandgap perovskite solar cell, from bottom to top, consists of 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 including the following steps: (1) A hole transport layer is prepared on an ITO conductive substrate; (2) A wide-bandgap perovskite thin film is prepared on the hole transport layer using the preparation method described in claim 1, so as to serve 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 inverted perovskite solar cell.

Images