Dynamic Simulation Of Hole Transporting Material In Perovskite Solar Cells

Perovskite solar cells as a new type of all-solid-state thin-film batteries,because of its rapid development of efficiency and become a renewable energy research hotspot.The hole transporting material is one of the important components of the perovskite solar cell,which has the function of optimizing the interface and adjusting the matching of the energy level,which is helpful to obtain the higher energy conversion efficiency.Although spiro-OMe TAD has high photoelectric conversion efficiency,it is difficult to prepare and expensive,so researchers try to find a cheap and efficient hole transport material instead of spiro-OMe TAD.For a long time,polythiophene-based hole-transporting materials have attracted much attention because of their good film-forming properties and high hole mobility,as well as good molecular design characteristics.The introduction of sulfur atoms,the length of the substituent chain and the length of the molecular chain can significantly affect the molecular interactions and thus affect the packing ways of materials,and ultimately affect the charge transfer rate.On the one hand,due to limited crystal structure data,the study of the relationship between molecular structure-spatial stacking mode-charge mobility of hole-transporting materials is hindered,and limited the rational design of high carrier transport efficiency materials;on the other hand,the in-depth study on the relationship between the molecular structure of polythiophene and its assembled form is the fundamental way to improve the charge transfer efficiency of the materials.In addition,the reorganization energy is the key parameter to calculate the charge transfer rate,the smaller the reorganization energy,the more favorable the charge transfer rate.Molecular stacking makes the twist angle of the system molecule less than that of the isolated molecule,and the reorganization energy can be reduced.In this work,the molecular dynamics simulation and QM /MM method were used as the main research methods.The system molecular dynamics(MD)simulation and the calculation of the system reorganization energy of polythiophene system with different sizes and unsubstituted,methyl(-CH3)and ethyl(-C2H5)substituted thiophene ring side chains were studied.Aimed at clarity:(1)A new approach to the spatial stacking mode of polythiophene organic photoelectric materials is proposed from the initial structure of random distribution,(2)the self-assembly of polythiophene system and the influence of side chain substitution on the self-assembly of the system,(3)molecular sizes and influence of substituents on the structure reorganization energy.Chapter 1 systematically summarizes the research status and backgrounds concerned to our work.Chapter 2 mainly introduces the methods of moleculardynamics and quantum mechanics.Chapter 3 to 5 are the main portion of our paper.In Chapter 3,the molecular dynamics simulation is used as the main research method to construct the amorphous system of oligothiophene molecules with different lengths.The molecular dynamics simulation is carried out for a long time to explore its self-assembly process and compare with the crystal structure,aims to find an accurate and effective method to locate the spatial stacking mode of organic photoelectric materials.In Chapter 4,the influence of different substituents(-CH3,-C2H5)on the spatial stacking mode of thiophene hole transporting materials was discussed.The assembly morphology and the stability of the assembly process were compared.The aim of this study is to find out the influence of thiophene ring side chain substitution on the system.In Chapter 5,we use quantum mechanics and molecular mechanics to calculate the reorganization energy,and investigate the influence of chain bending and flat structure on the reorganization energy.The influence of molecular size and different substituents on the reorganization energy is also discussed.Chapter 6 is summary and prospect.In this work,the relationship between molecular self-assembly and macroscopic properties is expected to promote the understanding of the electrical properties of PV devices,which lays a theoretical foundation for further rational selection and design of a hole transporting material having an excellent carrier transport efficiency,and it is of great significance to further promote the photovoltaic properties of perovskite solar cells.