Study On Defects Regulation,energy Level Regulation And Photoelectric Performance Of All Inorganic CsPbBr₃ Perovskite Solar Cells

All inorganic CsPbBr₃ perovskite solar cells have attracted lots of attention due to the superior stability.In this paper,the photoelectric conversion efficiency and stability of all inorganic CsPbBr₃ PSCs are improved by passivating the defects and regulating the energy level structure of all inorganic CsPbBr₃ PSCs.First,the effects of g-C₃N₄ on the microstructure of perovskite films,the trap density of Pb²⁺and the photoelectric properties of PSCs were studied.Secondly,the nanometer Co₃O₄ is used to regulate the level matching degree of CsPbBr₃/carbon electrode（CE）interface to improve the efficiency of hole extraction.Finally,the effects of additive Cd Br₂ on the passivation and regulation of bromine vacancy V_Br defect at the grain boundary on perovskite surface and on the photoelectric performance of the cells.The lamellar g-C₃N₄ nanomaterials were synthesized by heat treatment and the all inorganic PSCs with the structure of FTO/c-TiO₂/m-TiO₂/CsPbBr₃:g-C₃N₄/Carbon electrode（CE）were synthesized by multi-step spin-coating technique.The effects of g-C₃N₄ on the crystal structure of perovskite and photoelectric properties of PSCs were investigated.The results show that the optimal PCE of CsPbBr₃:g-C₃N₄ perovskite device was significantly increased from 5.85%to 8.00%and unencapsulated devices exhibit excellent long-term stability.This is because of the incorporation of g-C₃N₄additives to obtain low surface roughness and large particle size of CsPbBr₃ perovskite film,decreases the internal defect density via passivating the Pb²⁺dangling bonds around the crystal boundaries,as an energy barrier can effectively prevent the back electrons from recombination of holes at the carbon interface.The Co₃O₄ nanocrystalline were synthesized via chemical precipitation method and the all inorganic PSCs with the structure of FTO/c-TiO₂/m-TiO₂/CsPbBr₃/Co₃O₄/CE were synthesized by multi-step spin-coating technique,and the effect of energy level structure on the photoelectric properties of PSCs was studied.The results show that the optimized device basedon Co₃O₄ intermediate layer delivers a PCE of 8.92%,Co₃O₄ buffer layer can effectively improve the hole extraction rate,at the same time,the conduction band level of Co₃O₄ is higher than that of CsPbBr₃.As an energy barrier,Co₃O₄ can effectively prevent the recombination of reverse electrons and holes.The all PSCs with the structure of FTO/c-TiO₂/m-TiO₂/Cd Br₂-CsPbBr₃/CE were synthesized via a multi-step spin-coating technique.The results show that the photoelectric conversion efficiency of the devices were improved to 8.19%.This is attributed to the Cd Br₂fills the Br vacancy defect on the surface of perovskite crystal and Cd²⁺partially replaces Pb²⁺which have a large ion radius to obtain a highly stable perovskite crystal structure,which effectively reduces the density of defect states and improves the extraction efficiency of carrier.