Study On The Electron Transport Layer And Light Absorption Layer Of High-efficiency Perovskite Solar Cell Regulated By Ionic Liquid Materials

Over the past decade,organic-inorganic hybrid perovskite solar cells have attracted much attention.The conversion efficiency has been rapidly increased from 3.8%in 2009 to 25.2%in2020 due to their excellent photoelectric performance.However,the light absorption layer in the perovskite solar cell is easily decomposed by the influence of environmental humidity,resulting in rapid attenuation.Ionic liquid materials have exhibited the good application effects in the efficiencies and stabilities of perovskite solar cells.The electron transfer layer and the perovskite light absorption layer are the key factors that affect the photovoltaic performance of the PSC devices.Regulations and optimazations on the electron transfer layer and the perovskite light absorption layer have been proved to be the effective strategies to improve the efficiencies and stabilities of perovskite solar cells.In this work,the high-efficient electron transport layer and light absorption layer of perovskite solar cells were developed based on the regulation and optimization of ionic liquid materials.The research contents and innovations are as follows.1.A systematic study was carried out to control the electron transport layer of perovskite solar cells by introducing ionic liquid materials.In view of the problems of high temperature conditions and complex processes in the preparation of traditional electron transport materials,we developed the in situ microwave method to directly prepare the electron transport materials on the FTO by introducing the ionic liquids.This method can obtain the high-quality electron transport layers in low temperature with several minites and improve the photoelectric efficiency of perovskite solar cells.The effects of two ionic liquids with the same anion and different cations?[BMIM]NTF₂ and[HOOCMMIM]NTF₂?on the performance of the electron transport layer were investigated.Compared with TiO₂ and TiO₂-[BMIM]NTF₂,the introduction of[HOOCMMIM]NTF₂ increased the wettability of the interface of the electron transport layer,which is conducive to the formation of a continuous and dense perovskite film.The absorption intensity of the entire visible light region between 400-800 nm has been greatly improved.At the same time,the fluorescence intensity of the electron transport layer based on the TiO₂-[HOOCMMIM]NTF₂ is weakened and the fluorescence lifetime is shortened,indicating a faster electron transfer process.2.The research on doping pyridine carboxylic acid materials to control the light absorption layer of perovskite solar cells were carried out.The additives can effectively resolve the stability problem of the perovskite light absorption layer and the current and voltage hysteresis.We introduced the pyridine carboxylate additives into the CH₃NH₃PbI₃ light absorption layer.Four additives with better effects are selected,which are 2-pyridinecarboxylic acid,4-pyridinecarboxylic acid,2,2'-bipyridine-3,3'-dicarboxylic acid and 2,2'-bipyridine-4,4'-dicarboxylic acid.They can effectively improve the surface morphology and coverage of perovskite films.By optimizing the doping conditions of additives,the photoelectric conversion efficiencies reached 18.66%?the highest?,18.17%,16.5%and 17.19%,respectively.Compared with the photoelectric conversion efficiency?16.14%?of the original device without additive doping,the photoelectric conversion efficiency of the perovskite device with 2-picolinic acid was improved by about 15.6%.The results showed that the N atoms and carboxyl grouops of pyridine and the Pb atom of perovskite form a coordination bond.Thus,the additive-doped perovskite film is more uniform and denser.The absorption intensities in the visible light region of 400-700 nm are significantly improved,as well as the short-circuit current density of the corresponding device.The mechanism investigation showed that doping pyridine carboxylate additives can effectively improve the interface contact between the perovskite light absorption layer and the TiO₂ electron transport layer,improve the extraction ability of electrons and reduce the excited state electrons and the recombination of holes.Thus,the photoelectric conversion efficiencies of the perovskite solar cells can be greatly improved.