The Study Of Fabrication And Performance For All-inorganic Perovskite Solar Cells

Perovskite materials have excellent photochemical properties and are favored by many optoelectronic devices.The power conversion efficiency（PCE）of a new generation of solar cells employed perovskite as a light-absorbing layer has exceeded 25%,demonstrating the huge potential application of perovskite solar cells（PSCs）.There are many types of PSCs,and currently the most efficient ones are organic-inorganic hybrid cells.However,they suffer from the volatile of organic components under high temperature conditions,poor thermal stability and chemical stability,and easy reaction with oxygen,which hinders its further commercial application.All-inorganic perovskite solar cells with inorganic cations Cs⁺replacing organic components have overcome the above stability problems to a certain extent,and has attracted extensive attention at home and abroad.The efficiency of the cells has been increased from 2.9%in 2015 to 19%in 2020.Although there is still a gap with organic-inorganic PSCs,its potential development cannot be underestimated.Among various types of perovskite materials,CsPbBr₃ perovskite is the most excellent in stability,especially in humidity stability.In this paper,a new method of two-step spin-coating is proposed for the obvious shortcomings of various preparation methods of CsPbBr₃ perovskite film in the past.The use of CH₃OH and H₂O as the mixed solvent of CsBr greatly increased the solubility of CsBr,and the introduction of post-treatment solvent isopropanol（IPA）reduced the decomposition of the perovskite film.By optimizing experimental conditions,the PSCs based on planar CsPbBr₃ perovskite and without hole transporting layer finally obtained a PCE of 8.11%.The post-treatment solvent plays an important role in forming high quality perovskite absorbing layer.The perovskite film treated with IPA has a dense morphology.The density of defect states is also greatly reduced,which suppresses the recombination of carriers.At the same time,the cells also showed good humidity and temperature stability.Due to the appropriate band gap and relatively high stability,CsPbI₂Br solar cells have also been extensively studied.In this paper,trace polymer polyethylene glycol（PEG）is used as a perovskite precursor additive to increase the nucleation sites,promote the crystallization process of CsPbI₂Br,and effectively passivate the defects of the film.Compared with the 10.16%efficiency without additives,the PEG-added cells significantly improved efficiency to 13.70%,because the smooth and reduced grain boundary perovskite film reduces non-radiative recombination and is more conducive to the hole transport materials contact.The stability of unpackaged cells is also greatly improved.Moreover,the effect of additives on the perovskite film formation under low temperature conditions was studied.The results show that the addition of PEG is more efficient to the improvement of PSCs performance when the annealing temperature is reduced,and the efficiency is increased from 8.16%to 11.20%.This work proves that the polymer PEG can passivate the all-inorganic perovskite,which provides a new idea for improving the efficiency of the CsPbI₂Br cells.