Enlarging Crystal Grains To Enhance The Efficiency Of Perovskite Solar Cells Using Ionic Liquid

Organic-inorganic hybrid perovskites have been intensively studied since the first Perovskite Solar Cell PSC was reported in 2009,have long exciton diffusion length and excellent light absorption properties and their easy fabrication processes mean that they are among the most promising photoactive materials for next-generation solar cells.However,several problems associated with the use of perovskite materials still need to be addressed,such as their weak absorption in the visible region,pinholes or voids in their morphologies and high recombination rates.The grain boundaries of perovskite polycrystalline are defect region that not only provides carrier recombination sites but also introduces device degradation pathways.Efforts to enlarging the grain size of perovskite film and reducing its grain boundary are crucial for highly efficient and stable PSCs.In this report,using 1-Butyl-3-methylimidazolium tetrafluoroborate?BMIMBF₄?,dramatically enlarged the grain size of perovskite film and it reduced the rate of recombination and grain boundaries.We find that the ionic liquid BMIMBF₄ helps to reduce the activation energy for grain boundary migration and facilitate the grain growth,leading to significantly enlarged grain in the perovskite film.This article mainly studies the microstructure of perovskite thin film.We use BMIMBF₄ in different perovskite molecules such as:1.In MAPbI₃ perovskite,ionic liquid enhanced the film stability and also,I-V characteristics.We noted that efficiency of ionic liquid devices enhanced to 17.8%from14.2%?control device?.Ionic liquid devices are more stable than control devices.We checked the stability of the device for 250 hours.The control device reduces faster than ionic liquids.Using of ionic liquid enhanced the grain size and lead the devices for better performance.2.In(FA_0.83MA_0.17)_0.95Cs_0.05Pb(I_0.9Br_0.1)₃ perovskite,the grain size appeared more larger than MAPbI₃ and stability of ionic liquid device is much better.We noted the efficiency of ionic liquid device enhanced to 20.4%from 19.1%?control device?.Using of ionic liquid made surface much smoother and highly oriented planes.We proposed the use of BMIMBF₄ is an effective strategy to prepare high-efficiency planar perovskite solar cells.