Perovskite heterojunction and preparation method thereof
By constructing a heterojunction structure that encapsulates a narrow-bandgap perovskite single crystal with a wide-bandgap perovskite single crystal, the problems of surface defects and environmental impact in perovskite materials are solved, thereby improving device performance and the accuracy of information acquisition.
Patent Information
- Application Number
- CN202310199928.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-03-02
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2043-03-02
AI Technical Summary
Surface defects in perovskite materials are easily affected by factors such as preparation method, ambient humidity, and growth temperature, leading to a decline in device performance. Furthermore, they are easily degraded by oxygen, water vapor, and light when exposed to air. Existing passivation schemes for 'core-shell' structures are insufficient.
A heterojunction structure is prepared by wrapping a narrow-bandgap perovskite single crystal with a wide-bandgap perovskite single crystal, using a reverse temperature crystallization method. The outer perovskite layer protects the inner layer, isolates oxygen and water vapor, and passivates surface defects.
It significantly improves the crystal properties of perovskite single crystals, inhibits degradation caused by environmental factors, accurately obtains inner layer information, reduces fabrication costs, and enhances device performance.
Smart Images
Figure CN116096104B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optoelectronic device technology, and in particular to a perovskite heterojunction and its preparation method. Background Technology
[0002] Perovskite materials have attracted widespread attention from scientists and industry due to their advantages such as high carrier mobility, long carrier lifetime, and high absorption coefficient, sparking a research boom. Currently, perovskite materials are widely used in optoelectronic fields such as solar cells, light-emitting diodes, photodetectors, and field-effect transistors.
[0003] Defects in perovskite materials are a key factor affecting perovskite devices; therefore, passivating perovskite materials is of great significance for improving their performance. Defects in perovskite materials can be categorized into internal point defects, grain boundary defects, and surface defects. Internal defects are easily affected by factors such as fabrication methods, environmental humidity, and growth temperature. By adjusting these parameters, point defects can be effectively controlled. Compared to polycrystalline perovskite thin films, single-crystal perovskite materials can eliminate grain boundary defects and improve device performance; therefore, developing single-crystal perovskite devices is a current trend. For single-crystal perovskite materials, surface defects are one of the key factors affecting device performance. Furthermore, these single-crystal materials are easily degraded by oxygen, water vapor, and light when exposed to air, thus affecting device performance. Therefore, passivating surface defects in single crystals and isolating them from the effects of oxygen and water vapor are effective ways to improve the optoelectronic performance of perovskite devices.
[0004] Growing a wide-bandgap semiconductor on the surface of a narrow-bandgap semiconductor to form a core-shell structure with a first-type bandgap is an important way to passivate surface defects in semiconductor materials. For perovskite single crystals, growing a heterogeneous perovskite layer on its surface can passivate surface defects of the inner perovskite to a certain extent if the lattice structure of the inner perovskite is similar to that of the outer perovskite shell. At the same time, the outer perovskite shell acts as a protective layer, isolating it from the influence of water and oxygen. However, currently, perovskite passivation schemes based on the core-shell structure are still relatively lacking.
[0005] In view of this, the present invention proposes a novel perovskite heterojunction structure, the main structure of which is a wide-bandgap perovskite encapsulating a narrow-bandgap perovskite. Summary of the Invention
[0006] The purpose of this invention is to provide a perovskite heterojunction and its preparation method. The perovskite heterojunction structure can effectively inhibit the degradation of the inner crystal surface by environmental factors, and at the same time, it can passivate the surface defects of the inner crystal to a certain extent, thereby improving its crystal performance.
[0007] In a first aspect, the present invention provides a perovskite heterojunction comprising a narrow bandgap perovskite single crystal and a wide bandgap perovskite single crystal, wherein the wide bandgap perovskite single crystal is loaded on the surface of the narrow bandgap perovskite single crystal; wherein the bandgap of the narrow bandgap perovskite single crystal material is 2.21 eV-2.34 eV, and its corresponding fluorescence peak position is 560 nm-530 nm, and the bandgap of the wide bandgap perovskite single crystal material is 2.91 eV-3.29 eV, and its corresponding fluorescence peak position is 405 nm-375 nm.
[0008] Perovskite single crystal surfaces are often subject to various defects due to fabrication methods or operating environments, such as vacancy defects and doping defects. Furthermore, during operation, they are continuously affected by oxygen, water vapor, and light in the working environment, leading to structural degradation and consequently impacting device performance. Therefore, there is an urgent need to develop a perovskite heterojunction structure that can maintain the surface quality of perovskite single crystals, passivate surface defects, and isolate them from the effects of oxygen and water vapor.
[0009] The perovskite heterojunction structure of this invention is a perovskite heterojunction in which a wide-bandgap perovskite single crystal encloses a narrow-bandgap perovskite single crystal. The outer perovskite layer has a wider bandgap, while the inner perovskite layer has a narrower bandgap. Therefore, compared to the inner perovskite layer, the absorption wavelength range of the outer perovskite layer is narrower. By selecting a suitable wavelength for laser excitation, interference from the outer perovskite layer can be avoided, and the information from the inner perovskite layer can be directly obtained. Therefore, the perovskite heterojunction structure of this invention not only maintains the surface quality of the perovskite single crystal and passivates surface defects, but also effectively isolates the influence of oxygen and water vapor, significantly improving its crystal performance.
[0010] To facilitate accurate acquisition of information about the inner perovskite, when selecting narrow-bandgap perovskite single-crystal materials and wide-bandgap perovskite single-crystal materials, it is preferable that the bandgap difference can support the absence of spectral overlap between the two materials with different bandgap. The bandgap of the narrow-bandgap perovskite single-crystal material is 2.21 eV-2.34 eV, with corresponding fluorescence peak positions of 560 nm-530 nm, while the bandgap of the wide-bandgap perovskite single-crystal material is 2.91 eV-3.29 eV, with corresponding fluorescence peak positions of 405 nm-375 nm.
[0011] This invention does not strictly limit the specific materials used for narrow-bandgap perovskites and wide-bandgap perovskites, only requiring that the bandgap difference between the two meets the requirements of the characterization method. Specifically, the narrow-bandgap perovskite single-crystal material includes any one of CsPbBr3, MAPbBr3, and FAPbBr3, wherein the bandgap of CsPbBr3 is 2.34 eV, the bandgap of MAPbBr3 is 2.26 eV, and the bandgap of FAPbBr3 is 2.21 eV. The wide-bandgap perovskite single-crystal material includes any one of MAPbCl3, FAPbCl3, and CsPbCl3, wherein the bandgap of MAPbCl3 is 3.06 eV, and the bandgap of FAPbCl3 is 3.29 eV.
[0012] Secondly, the present invention also discloses a method for preparing the above-mentioned perovskite heterojunction, comprising the following steps:
[0013] First, narrow-bandgap perovskite single crystals were prepared using the inverse temperature crystallization method. Then, wide-bandgap perovskite single crystals were constructed on the surface of the narrow-bandgap perovskite single crystals to prepare a wide-bandgap perovskite single crystal encapsulating a narrow-bandgap perovskite heterojunction.
[0014] In the method for preparing the perovskite heterojunction of the present invention, a narrow-bandgap perovskite single crystal is first prepared by inverse temperature crystallization. Then, a wide-bandgap perovskite single crystal is constructed on the surface of the narrow-bandgap perovskite single crystal using the same method, so that the wide-bandgap perovskite coats the outside of the narrow-bandgap perovskite, forming a wide-bandgap perovskite single crystal-encapsulated narrow-bandgap perovskite heterojunction. This preparation method has the advantages of short cultivation cycle, low preparation cost, and high product quality.
[0015] As a preferred embodiment of this technical solution, the narrow bandgap perovskite single crystal is prepared by heating the narrow bandgap perovskite precursor solution at 80-90℃ for 3-5 days to precipitate perovskite crystals by increasing the solution temperature and reducing solubility, thereby obtaining narrow bandgap perovskite single crystals.
[0016] The narrow bandgap perovskite single crystal material of the present invention includes any one of CsPbBr3, MAPbBr3 and FAPbBr3 with a bandgap of 2.21eV-2.34eV. Therefore, in the preparation of the narrow bandgap perovskite precursor solution, the organic solution of the raw material mixture can be stirred at 20-30°C for 10-15h to fully dissolve it, and then filtered to obtain the narrow bandgap perovskite precursor solution, wherein the molar ratio of Cs source, Pb source and Br source is 1:(1-2):(3-5). For example, when preparing a narrow bandgap perovskite CsPbBr3 precursor solution, an organic solution of a mixture of Cs source, Pb source and Br source can be stirred at 20-30℃ for 10-15h, and then filtered to obtain a narrow bandgap perovskite precursor solution. The Cs source, Pb source and Br source can be selected as CsBr and PbBr2. In this case, the molar ratio of CsBr and PbBr2 is preferably 1:(1-2).
[0017] After obtaining a narrow-bandgap perovskite single crystal, a wide-bandgap perovskite single crystal is constructed on the surface of the narrow-bandgap perovskite single crystal using a reverse-temperature crystallization method. The narrow-bandgap perovskite single crystal is placed in a wide-bandgap perovskite precursor solution and heated at 45-55℃ for 3-5 days. The wide-bandgap perovskite continuously precipitates and crystallizes on the surface of the narrow-bandgap perovskite, thus obtaining a wide-bandgap perovskite single crystal encapsulating a narrow-bandgap perovskite heterojunction.
[0018] The wide-bandgap perovskite single-crystal material of the present invention includes any one of MAPbCl3, FAPbCl3, and CsPbCl3 with a bandgap of 2.91 eV-3.29 eV. For example, in preparing the wide-bandgap perovskite MAPbCl3 precursor solution, an organic solution of a mixture of MA source, Pb source, and Cl source can be stirred at 20-30°C for 0.5-1 h, and then filtered to obtain the wide-bandgap perovskite precursor solution. The MA source, Pb source, and Cl source can be selected from MACl and PbCl2, and the molar ratio of MACl to PbCl2 is preferably 1:(1-2).
[0019] As a preferred embodiment of this technical solution, the concentration of the organic solution is 0.5-1.5M, and the organic solvent used includes any one of DMSO, DMF, and GBL.
[0020] The perovskite heterojunction of the present invention has at least the following technical advantages compared with the prior art:
[0021] 1. The perovskite heterojunction structure of this invention consists of a wide-bandgap perovskite single crystal encapsulating a narrow-bandgap perovskite single crystal. Because the outer perovskite has a wider bandgap, its absorption wavelength range is narrower than that of the inner narrow-bandgap perovskite. Therefore, by selecting a suitable laser excitation band, interference from the outer perovskite information can be avoided, and the information of the inner perovskite can be directly obtained. Simultaneously, because the outer perovskite can protect the inner perovskite, it can passivate surface defects of the inner perovskite to a certain extent and isolate the influence of water vapor and oxygen in the working environment. Therefore, the performance of the internal crystal can be studied more accurately, thus providing a new approach for the fabricated devices.
[0022] 2. The perovskite heterojunction structure of the present invention can effectively inhibit the degradation of the inner crystal surface by environmental factors, and can passivate the surface defects of the inner crystal to a certain extent, thereby improving its crystal performance.
[0023] 3. The method for preparing perovskite heterojunctions of the present invention has the advantages of short cultivation cycle, low preparation cost and good product quality. Attached Figure Description
[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0025] Figure 1 The fluorescence spectra of the MAPbCl3 (left) and CsPbBr3 (right) materials of this invention are shown.
[0026] Figure 2 The images show the CsPbBr3 material of this invention (left) and the core-shell structured material of CsPbBr3 after treatment (right).
[0027] Figure 3 The images show the XRD patterns (left) and some details (right) of the MAPbCl3 and CsPbBr3 core-shell structures of this invention. Detailed Implementation
[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0029] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0031] Example 1
[0032] A mixture of CsBr and PbBr2 in a 1:2 molar ratio was dissolved in DMSO, with the solution concentration controlled at 1M. The mixture was stirred overnight at room temperature. The stirred solution was filtered to obtain a clear precursor solution. The precursor solution was placed on a heating stage and heated at 80-90℃ for 3-5 days to obtain CsPbBr3 perovskite single crystals.
[0033] A mixture of MACl and PbCl2 in a 1:1 molar ratio was dissolved in DMF, with the solution concentration controlled at 1M. The mixture was stirred at room temperature for 30 minutes, and the stirred solution was filtered to obtain a clear MAPbCl3 precursor solution.
[0034] Place the MAPbCl3 precursor solution on a heating stage and heat it at 45-55℃ for 3-5 days until MAPbCl3 single crystals appear. Filter the solution again to obtain a clear precursor solution, ensuring that the MAPbCl3 precursor solution is saturated.
[0035] CsPbBr3 perovskite single crystals are placed in a saturated MAPbCl3 precursor solution and heated on a heating stage at 45-55℃ for 3-5 days. A transparent single crystal shell can be observed growing on the surface of the CsPbBr3 perovskite single crystal. The perovskite heterojunction single crystal can then be obtained by removing the shell.
[0036] Example 2
[0037] A mixture of MABr and PbBr2 in a 1:1 molar ratio was dissolved in DMF, with the solution concentration controlled at 1M. The mixture was stirred at room temperature for 2 hours. The stirred solution was then filtered to obtain a clear precursor solution. The precursor solution was placed on a heating stage and heated at 55°C for 3-5 days to obtain MAPbBr3 perovskite single crystals.
[0038] A mixture of MACl and PbCl2 in a 1:1 molar ratio was dissolved in DMF, with the solution concentration controlled at 1M. The mixture was stirred at room temperature for 30 minutes, and the stirred solution was filtered to obtain a clear MAPbCl3 precursor solution.
[0039] Place the MAPbCl3 precursor solution on a heating stage and heat it at 45-55℃ for 3-5 days until MAPbCl3 single crystals appear. Filter the solution again to obtain a clear precursor solution, ensuring that the MAPbCl3 precursor solution is saturated.
[0040] Place the MAPbBr3 perovskite single crystal in a saturated MAPbCl3 precursor solution and heat it on a heating stage at 45-55℃ for 3-5 days. A transparent single crystal shell can be observed growing on the surface of the MAPbBr3 perovskite single crystal. The perovskite heterojunction single crystal can then be obtained by removing it.
[0041] Example 3
[0042] A mixture of FABr and PbBr2 in a 1:1 molar ratio was dissolved in a 1:1 mixture of GBL and DMF solutions, with the solution concentration controlled at 1M. The mixture was stirred at room temperature for 2 hours. The stirred solution was then filtered to obtain a clear precursor solution. The precursor solution was placed on a heating stage and heated at 60°C for 3-5 days to obtain FAPbBr3 perovskite single crystals.
[0043] A mixture of MACl and PbCl2 in a 1:1 molar ratio was dissolved in DMF, with the solution concentration controlled at 1M. The mixture was stirred at room temperature for 30 minutes, and the stirred solution was filtered to obtain a clear MAPbCl3 precursor solution.
[0044] FAPbBr3 perovskite single crystals are placed in a MAPbCl3 precursor solution and heated on a heating stage at 45-55℃ for 3-5 days. A transparent single crystal shell can be observed growing on the surface of the FAPbBr3 perovskite single crystal. The perovskite heterojunction single crystal can then be obtained by removing the shell.
[0045] Compare with Example 1
[0046] A mixture of CsBr and PbBr2 in a 1:2 molar ratio was dissolved in DMSO at a concentration of 1 M. The solution was stirred overnight at room temperature. The stirred solution was then filtered through a 0.22 μm filter to obtain a clear precursor solution. The precursor solution was then placed on a heating plate and heated at 80-90 °C for 3-5 days to obtain CsPbBr3 perovskite single crystals.
[0047] In Example 1 of this invention, a wide-bandgap perovskite single crystal encapsulating a narrow-bandgap perovskite heterojunction was prepared using MAPbCl3 (wide bandgap, approximately 3.07 eV) and CsPbBr3 (narrow bandgap, approximately 2.34 eV), materials with a certain bandgap difference. Figure 1 It can be seen that the fluorescence peak position of MAPbCl3 material is about 405 nm, and the fluorescence peak position of CsPbBr3 material is about 530 nm. The spectra of the two do not overlap and will not affect the characterization of the inner narrow bandgap perovskite.
[0048] Depend on Figure 2 As can be seen in the right image, the surface of the CsPbBr3 material is coated with a layer of transparent MAPbCl3. Meanwhile, in... Figure 3 The XRD pattern shows that the core-shell structure exhibits diffraction peaks similar to those of MAPbCl3, and at the same diffraction angle, diffraction peaks similar to those of CsPbBr3 can also be observed. This indicates that the surface of CsPbBr3 is coated with MAPbCl3.
[0049] To further investigate the lifetime of wide-bandgap perovskite single crystals encapsulating narrow-bandgap perovskite heterojunctions, transient fluorescence lifetime spectra of CsPbBr3 material (Control Example 1) and CsPbBr3 core-shell structure (CsPbBr3-Coreshell, Example 1) were tested.
[0050] After processing CsPbBr3 material to form a core-shell structure, the test results showed that its transient fluorescence lifetime was significantly improved. This further indicates that MAPbCl3 material passivates the surface defects of CsPbBr3 material, which is more beneficial to the performance of its devices.
[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a perovskite heterostructure, characterized in that, Includes the following steps: First, narrow bandgap perovskite single crystals were prepared using the reverse temperature crystallization method. Then, wide bandgap perovskite single crystals were constructed on the surface of the narrow bandgap perovskite single crystals to prepare a wide bandgap perovskite single crystal encapsulating a narrow bandgap perovskite heterojunction. In the preparation of the narrow bandgap perovskite single crystal, the narrow bandgap perovskite precursor solution is heated at 80-90 ℃ for 3-5 days to obtain the narrow bandgap perovskite single crystal. When constructing a wide-bandgap perovskite single crystal on the surface of a narrow-bandgap perovskite single crystal, the narrow-bandgap perovskite single crystal is placed in a wide-bandgap perovskite precursor solution and heated at 45-55 ℃ for 3-5 days to obtain a wide-bandgap perovskite single crystal encapsulating a narrow-bandgap perovskite heterojunction. The perovskite heterojunction includes a narrow bandgap perovskite single crystal and a wide bandgap perovskite single crystal, and the wide bandgap perovskite single crystal is loaded on the surface of the narrow bandgap perovskite single crystal. The narrow bandgap perovskite single crystal material has a bandgap of 2.21 eV-2.34 eV, with corresponding fluorescence peaks of 560 nm-530 nm; the wide bandgap perovskite single crystal material has a bandgap of 2.91 eV-3.29 eV, with corresponding fluorescence peaks of 405 nm-375 nm. The narrow bandgap perovskite single crystal material includes any one of CsPbBr3, MAPbBr3 and FAPbBr3; The wide-bandgap perovskite single crystal material is MAPbCl3.
2. The preparation method according to claim 1, characterized in that, The narrow bandgap perovskite precursor solution is prepared by stirring an organic solution of a mixture of Cs, Pb, and Br sources at 20-30 °C for 10-15 h, followed by filtration to obtain the narrow bandgap perovskite precursor solution. The molar ratio of Cs source, Pb source and Br source is 1:(1-2):(3-5).
3. The preparation method according to claim 2, characterized in that, The wide-bandgap perovskite precursor solution is prepared by stirring an organic solution of a mixture of MA source, Pb source and Cl source at 20-30 °C for 0.5-1 h, followed by filtration to obtain the wide-bandgap perovskite precursor solution. The molar ratio of MA source, Pb source and Cl source is 1:(1-2):(2-4).
4. The preparation method according to claim 2 or 3, characterized in that, The concentration of the organic solution is 0.5-1.5M, and the organic solvent used includes any one of DMSO, DMF and GBL.