Defect regulation and control method for improving phase stability of inorganic perovskite CsPbI3

Abstract

The invention discloses a defect regulation and control method for improving the phase stability of inorganic perovskite CsPbI3, and the method comprises the steps: firstly constructing different defect models for CsPbI3, carrying out the structural optimization of the defect models and an initial CsPbI3 structure, carrying out the calculation of a phase change barrier based on the optimized structure, determining the influence of the atom vacancy defect concentration on the stability, and carrying out the calculation of the phase change barrier. The method comprises the following steps: firstly, selecting a CsPbI3 model, then, carrying out metal ion doping replacement on the initial CsPbI3 model, carrying out structure optimization on the replaced model, finally, carrying out formation energy calculation on the optimized structure, and determining the optimal doped and replaced metal ion, thereby completing the defect regulation and control of the CsPbI3 phase stability. According to the scheme of the invention, based on the formation of the metal ions capable of determining the optimal doping and replacement of the inorganic perovskite CsPbI3 material, the optimal regulation and control of the defects of the inorganic perovskite CsPbI3 material are realized, the service life of the perovskite solar cell is remarkably prolonged, the solar cell is enabled to convert solar energy into electric energy more effectively, and the efficiency of the solar cell is improved. The power generation capability of the solar cell is improved, and the cost is effectively saved.

Description

Technical Field

[0001] The present invention belongs to the field of perovskite solar cells, and in particular relates to a defect control method for improving the phase stability of inorganic perovskite CsPbI3. Background Art

[0002] As human society progresses, the demand for energy is increasing. It's no exaggeration to compare the evolution of energy transformation to the evolution of humanity. Energy is the driving force behind social development, and energy issues have always been a key focus of human progress. Solar energy has become a major focus for many researchers, with solar cells being a particular focal point. Due to their excellent optoelectronic properties, lead-based halide perovskites are considered one of the preferred light-absorbing materials for next-generation solar cells. However, lead-based halide perovskites exhibit extremely poor phase stability under natural conditions and rapidly transform from a perovskite phase to a non-perovskite phase, significantly reducing their ability to absorb natural light and leading to a significant decrease in cell efficiency. This detrimental phase transition severely limits the effective lifespan of photovoltaic devices and their large-scale industrial application. Therefore, how to efficiently and significantly improve the phase stability of lead-based halide perovskites remains a pressing challenge in the field of perovskite solar cell research. Experimental work has revealed a close correlation between defects in lead-based halide perovskites and their phase stability, but our understanding of this issue remains largely lacking. Summary of the Invention

[0003] In view of the above problems, the object of the present invention is to provide a defect control method for improving the phase stability of inorganic perovskite CsPbI3.

[0004] The specific technical solutions for achieving the purpose of the present invention are as follows:

[0005] A defect control method for improving the phase stability of inorganic perovskite CsPbI3 comprises the following steps:

[0006] Step 1: construct different defect models for CsPbI3, and optimize the defect models and the initial CsPbI3 structure;

[0007] Step 2: Calculate the phase transition barrier based on the optimized structure to determine the effect of atomic vacancy defect concentration on stability;

[0008] Step 3: doping the initial CsPbI3 model with metal ions and optimizing the structure of the replaced model;

[0009] Step 4: Calculate the formation energy of the structure optimized in step 3 and determine the optimal metal ions to be doped and replaced, thereby completing the defect regulation of CsPbI3 phase stability.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The solution of the present invention is based on the formation of metal ions that can determine the optimal doping substitution for the inorganic perovskite CsPbI3 material, thereby achieving optimal regulation of the defects of the inorganic perovskite CsPbI3 material, significantly extending the life of the perovskite solar cell, allowing the solar cell to more efficiently convert solar energy into electrical energy, improving the power generation capacity of the solar cell and effectively saving costs.

[0012] The present invention will be further described below with reference to specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the process flow of the defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to the present invention.

[0014] Figure 2 Schematic diagram of energy change on the lowest energy barrier path of the CsPbI3 defect model containing one iodine vacancy (a total of 19 atoms) from the γ phase to the MS2 state in an embodiment of the present invention.

[0015] Figure 3 Schematic diagram of energy change on the lowest energy barrier path of the CsPbI3 defect model containing one iodine vacancy (39 atoms in total) from the γ phase to the δ phase in an embodiment of the present invention.

[0016] Figure 4 Schematic diagram of energy change on the lowest energy barrier path of the CsPbI3 defect model containing one iodine vacancy (79 atoms in total) from the γ phase to the δ phase in an embodiment of the present invention.

[0017] Figure 5 Schematic diagram of energy change curves on the phase transition path from γ phase to δ phase corresponding to CsPbI3 defect models of different sizes in an embodiment of the present invention.

[0018] Figure 6 is the V near the B-site doping ion calculated in the embodiment of the present invention I Formation energy (a) and diffusion barrier (b). DETAILED DESCRIPTION

[0019] A defect control method for improving the phase stability of inorganic perovskite CsPbI3 comprises the following steps:

[0020] Step 1: Construct different defect models for CsPbI3 and optimize the defect models and the initial CsPbI3 structure:

[0021] Step 1-1: First, construct the structural model of perovskite CsPbI3:

[0022] The number of atoms in the structural model of the perovskite CsPbI3 needs to be between 15 and 100.

[0023] Step 1-2: Delete certain atoms in the constructed perovskite CsPbI3 structure model and construct various defect models:

[0024] When the deleted atom is an iodine atom, the two Pb atoms adjacent to the iodine vacancy need to be moved closer together until the distance is less than or equal to

[0025] Steps 1-3: Optimize the structure of the constructed defect model and the initial perovskite CsPbI3 structure model respectively, that is, adjust the lattice size and atomic position within the model to find the structure with the lowest energy and complete the structural optimization;

[0026] Step 2: Calculate the phase transition barrier based on the optimized structure to determine the effect of atomic vacancy defect concentration on stability:

[0027] Based on the defect model after structural optimization, random potential energy surface walking reaction path sampling method SSW-RS and DFT calculations were performed to determine the phase transition paths of different defect models, thereby determining the influence of different atomic vacancy defect concentrations on the stability of perovskite CsPbI3.

[0028] Step 3: Replace the initial CsPbI3 model with metal ions and optimize the structure of the replaced model:

[0029] The initial CsPbI3 model was doped with B-site metal ions of different valence states, radii, and whether or not they contained lone pair electrons, and the structures of the models after metal ion replacement were optimized.

[0030] At the same time, ions inside the model rather than at the edge of the model are selected for replacement;

[0031] The process of structural optimization is to adjust the lattice size and atomic positions in the model, find the structure with the lowest energy, and complete the structural optimization.

[0032] Step 4: Calculate the formation energy of the structure optimized in step 3 and determine the optimal metal ions to be doped and replaced, thereby completing the defect control of CsPbI3 phase stability:

[0033] After structural optimization, the total energy and eigenvalues ​​of each model system can be obtained. The obtained eigenvalues ​​are Gaussian expanded to obtain the position of each defect energy level and the energy of the valence band top. The formation energy of each defect is determined according to the following formula:

[0034] ΔH f (D q)=E tot (D q )-E tot (bulk)-∑ i n i (μ i +E i )+q(E F +E VBM )

[0035] Among them E tot (bulk) is the total energy of the defect-free unit cell, E tot (D q ) is the total energy of the defect structure with q charge, μ i is the chemical potential of the defect atom, E i is the energy of a single defect atom, E F is the Fermi energy, E VBM It is the top of the price band;

[0036] After calculation, the V I The formation energy results are visualized, and the metal ion with the highest formation energy is the metal ion with the best defect regulation.

[0037] At the same time, in actual operation, when the vacancy defect is an iodine vacancy defect, the best doping replacement metal ion is a trivalent lanthanide ion.

[0038] With the iodine vacancy defect V I With the increase of concentration, iodine vacancy defects have a significant promoting effect on the phase transition process of perovskite CsPbI3. The replacement of B-site ions will affect the formation of iodine vacancy defects. The ideal B-site replacement metal cation must meet the following requirements: (1) no lone pair electrons, (2) as high a valence state as possible, (3) with Pb 2+ The difference in radius is small. However, the latter two requirements usually conflict with each other. Because metal cations with high valence (such as +4, +5, +6, +7) usually have smaller radius After replacing the appropriate metal cation, V I The formation energy has changed significantly.

[0039] Example

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] A defect control method for improving the phase stability of inorganic perovskite CsPbI3 comprises the following steps:

[0042] Step 1: Construct different defect models for CsPbI3 and optimize the defect models and the initial CsPbI3 structure:

[0043] Step 1-1: First, construct the structural model of perovskite CsPbI3:

[0044] In this example, Python was used to create POSCAR files for three CsPbI3 unit cells with 20, 40, and 80 atoms respectively.

[0045] Step 1-2: Delete certain atoms in the constructed perovskite CsPbI3 structure model and construct various defect models:

[0046] When the deleted atom is an iodine atom, the two Pb atoms adjacent to the iodine vacancy need to be moved closer together until the distance is less than or equal to

[0047] Steps 1-3: Structural optimization is performed on the constructed defect model and the initial perovskite CsPbI3 structure model respectively, that is, the lattice size and atomic position within the model are adjusted to find the structure with the lowest energy and complete the structural optimization.

[0048] In this example, the gam version of the VASP software package was used to perform DFT calculations to optimize the structure.

[0049] Vesta software was used to visualize the established model, and the number of atoms in the POSCAR file was deleted and the atomic coordinates below were deleted and added.

[0050] Upload the POSCAR file downloaded from Vesta to the calculation folder on the server, put KPOINTS into the calculation folder, and set the supercell size to 1*1*1.

[0051] Find the POTCAR file of I and copy it into a POTCAR file.

[0052] INCAR was set up with the following parameters: the electron wave function was expanded in a plane wave to a cutoff energy of 400 eV and a k-spacing of The k-mesh of Γ-Center is used to perform structural optimization and electronic structure calculations. The atomic positions and lattice parameters are optimized until the residual force converges to The number of electrons is modified to change the charge of the defect structure.

[0053] Perform structural optimization.

[0054] Copy the optimized CONTCAR file to a POSCAR file, and use the python script to modify lines 3-5 in the POSCAR file while multiplying it by the lattice scaling constant.

[0055] Change the ISIF parameter in INCAR to 2 and optimize the lattice constant and atomic position at the same time.

[0056] Step 2: Calculate the phase transition barrier based on the optimized structure to determine the effect of atomic vacancy defect concentration on stability:

[0057] Based on the defect model after structural optimization, random potential energy surface walking reaction path sampling method SSW-RS and DFT calculations were performed to determine the phase transition paths of different defect models, thereby determining the influence of different atomic vacancy defect concentrations on the stability of perovskite CsPbI3.

[0058] In this embodiment, the optimized model is subjected to SSW-RW calculation by the LASP program software nested in VASP to obtain all the minimum values ​​on the potential energy surface during the phase transition of perovskite CsPbI3. The two minimum points on the potential energy surface are used as starting points, and the search is carried out in the middle direction until they meet. The saddle point of the potential energy surface is then searched near the meeting point to finally determine the transition state and potential barrier.

[0059] The three types of V I Visualize the various transition states and potential barriers during the phase transition of the defect model.

[0060] Step 3: Replace the initial CsPbI3 model with metal ions and optimize the structure of the replaced model:

[0061] The initial CsPbI3 model was doped with B-site metal ions of different valence states, radii, and whether or not they contained lone pair electrons, and the structures of the models after metal ion replacement were optimized.

[0062] At the same time, ions inside the model rather than at the edge of the model are selected for replacement;

[0063] The process of structural optimization is to adjust the lattice size and atomic positions in the model, find the structure with the lowest energy, and complete the structural optimization.

[0064] In this example, Python was used to create a POSCAR file for a 160-atom CsPbI3 unit cell.

[0065] The structure was optimized using the same method as in step 1.

[0066] Step 4: Calculate the formation energy of the structure optimized in step 3 and determine the optimal metal ions to be doped and replaced, thereby completing the defect control of CsPbI3 phase stability:

[0067] After structural optimization, the total energy and eigenvalues ​​of each model system can be obtained. The obtained eigenvalues ​​are Gaussian expanded to obtain the position of each defect energy level and the energy of the valence band top. The formation energy of each defect is determined according to the following formula:

[0068] ΔH f (D q )=E tot (D q )-E tot (bulk)-∑ i n i (μ i +E i )+q(E F +E VBM )

[0069] Among them E tot (bulk) is the total energy of the defect-free unit cell, E tot (D q ) is the total energy of the defect structure with q charge, μ i is the chemical potential of the defect atom, E i is the energy of a single defect atom, E F is the Fermi energy, E VBM It is the top of the price band;

[0070] After calculation, the V I The formation energy results are visualized, and the metal ion with the highest formation energy is the metal ion with the best defect regulation.

[0071] At the same time, when the vacancy defect is an iodine vacancy defect, the optimal doping replacement metal ion is a trivalent lanthanide ion.

[0072] The established model was visualized using Vesta software, and the Pb 2+ ions are replaced by metal ions, and the replaced Pb 2+ Required to be inside the model.

[0073] After generating the POSCAR file, replace the original POSCAR file to generate a new POTCAR, and then calculate the formation energy. The formation energy is calculated according to the above formula based on the generated data.

[0074] The relationship between the formation energy of VI after substitution of 32 B-site metal ions with different valence states, radii, and whether or not they contain lone pair electrons is visualized to find the metal ion substitution that is most suitable for increasing the formation energy of VI.

[0075] from Figure 2 , Figure 3 and Figure 4 It can be seen that although different concentrations of iodine defect models will not change the overall phase transition path of CsPbI3, they change the phase transition process from γ phase to MS1. The greater the iodine defect concentration, the lower the phase transition barrier and the faster the phase transition process, which leads to a significant reduction in the service life of perovskite solar cells.

[0076] Figure 5 This is a summary of the energy barrier changes in the phase transition paths for three different iodine defect models and a defect-free model. The figure shows that the phase transition energy barrier for CsPbI3 in the defect-free model is significantly greater than that in the defect-free model, and the corresponding perovskite solar cell has a longer service life.

[0077] from Figure 6 It can be seen that whether the doped metal cation has lone pair electrons, valence state and ionic radius can have a huge impact on the VI formation energy.

[0078] The ideal metal cation doped at the B site must simultaneously meet the following requirements: (1) no lone pair electrons, (2) as high a valence state as possible, and (3) 2+ The difference in radius is small. The metal cations that can meet the above three requirements are usually +3, such as lanthanide metal ions La 3+ ,Ce 3+ In summary, doping with trivalent lanthanide metal cations can effectively inhibit the I The formation of ions can significantly improve the service life of perovskite solar cells.

[0079] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A defect control method for improving the phase stability of inorganic perovskite CsPbI3, characterized in that: The following steps are involved: Step 1: construct different defect models for CsPbI3, and optimize the defect models and the initial CsPbI3 structure; Step 2: Calculate the phase transition barrier based on the optimized structure to determine the effect of atomic vacancy defect concentration on stability; Step 3: doping the initial CsPbI3 model with metal ions and optimizing the structure of the replaced model; Step 4: Calculate the formation energy of the structure optimized in step 3 and determine the optimal metal ions to be doped and replaced, thereby completing the defect regulation of CsPbI3 phase stability.

2. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 1, characterized in that: The step 1 of constructing a defect model and performing structural optimization is as follows: Step 1-1, first construct the structural model of perovskite CsPbI3; Step 1-2: Deleting certain atoms from the constructed perovskite CsPbI3 structure model to construct defect models; Steps 1-3: Structural optimization is performed on the constructed defect model and the initial perovskite CsPbI3 structure model respectively, that is, the lattice size and atomic position within the model are adjusted to find the structure with the lowest energy and complete the structural optimization.

3. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 2, characterized in that: The number of atoms in the structural model of the perovskite CsPbI3 constructed in step 1-1 must be between 15 and 100.

4. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 2, characterized in that: When the atom deleted in step 1-2 is an iodine atom, the two Pb atoms adjacent to the iodine vacancy need to be moved closer to each other until the distance is less than or equal to 5. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 1, characterized in that: The influence of atomic vacancy defect concentration on stability is determined in step 2, specifically: Based on the defect model after structural optimization, random potential energy surface walking reaction path sampling method SSW-RS and DFT calculations were performed to determine the phase transition paths of different defect models, thereby determining the influence of different atomic vacancy defect concentrations on the stability of perovskite CsPbI3.

6. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 1, characterized in that: In step 3, the initial CsPbI3 model is doped with metal ions and the structure is optimized, specifically: The initial structure of the CsPbI3 model was replaced by B-site metal ions with different valence states, radii, and whether or not they contained lone pair electrons, and the structures of the models after metal ion replacement were optimized respectively.

7. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 6, characterized in that: The process of structural optimization is to adjust the lattice size and atomic positions in the model, find the structure with the lowest energy, and complete the structural optimization.

8. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 1, characterized in that: The determination of the optimal metal ion to be doped and replaced in step 4 is specifically as follows: After structural optimization, the total energy and eigenvalues ​​of each model system can be obtained. The obtained eigenvalues ​​are Gaussian expanded to obtain the position of each defect energy level and the energy of the valence band top. The formation energy of each defect is determined according to the following formula: ΔH f (D q )−E tot (D q )-AND tot (bulk)-∑ i n i (μ i +E i )+q(E F +E VBM ) Among them E tot (bulk) is the total energy of the defect-free unit cell, E tot (D q ) is the total energy of the defect structure with q charge, μ i is the chemical potential of the defect atom, E i is the energy of a single defect atom, E F is the Fermi energy, E VBM It is the top of the price band; After calculation, the V I The formation energy results are visualized, and the metal ion with the highest formation energy is the metal ion with the best defect regulation.

9. The defect control method for improving the phase stability of inorganic perovskite CsPbI3 according to claim 8, characterized in that: When the vacancy defect is an iodine vacancy defect, the best doping replacement metal ion is a trivalent lanthanide ion.

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