Fabrication of large columnar grains composed CsPbBr3 films for efficient solar cells through ligand engineering

Abstract

All inorganic perovskite of CsPbBr3 based perovskite solar cells (PSCs) have attracted increasingly attentions in the hot topics for research of PSCs owing to their high stability in air. Fabrication of columnar CsPbBr3 grains spanning the whole films is strongly desired for fabrication of highly efficient solar cells. Here, we introduce a polymer of polyethylene oxide (PEO) into PbBr2 solution as a ligand to modify the formation of CsPbBr3 films, and then promote the microstructure of CsPbBr3 films, which evolves from small grains to equiaxed large grains with preferred crystallographic orientation. The improved quality of CsPbBr3 films contributes to low defect density and prolonged life time of carriers. As a result, the efficiency of carbon-based hole transportation layer (HTL) free solar cell boosts from 5.92 % to 8.12 % by optimizing the volume fraction of PEO in PbBr2 solution.