Surface grain boundary passivation via mixed antisolvent and PC₆₁BM assistant for stable perovskite solar cells

Perovskite solar cells (PSCs) have attracted intense research interest in the last few years due to their excellent properties. However, the trap states at grain boundary (GBs) of perovskite films lead to charge recombination and perovskite film decomposition, which deteriorate the stability of PSCs. It has been demonstrated that the GBs passivation is an effective way to eliminate trap states and enhance the stability of PSCs. In this work, ethyl acetate (EA) and chlorobenzene (CB) were used as anti-solvent, mixing with phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) to replace pure antisolvent CB to control the GBs passivation of perovskite film. Meanwhile, enhanced interfacial hydrophobic characteristic effectively restricted the penetration of moisture. Correspondingly, with optimizing the volume ratio of EA/CB, the power conversion efficiency of PSCs based on CH₃NH₃PbI₃ increased from 14.4 to 16.1% and the stability is greatly improved. This shows the adoption of a mixed solvent for EA and CB contained PC₆₁BM as the solute can be used as an efficient tactic to passivate the surface crystal boundary, improve charge carrier transportation and device performance.