Surface Passivation of Perovskite Film by Small Molecule Infiltration for Improved Efficiency of Perovskite Solar Cells

Surface morphology of perovskite film is critical for highly efficient perovskite-based solar cells. The solution processed perovskite films tend to have voids and pin-holes between the crystals, which has been cited as very detrimental to device performance. The voids and pin-holes not only cause electrical shorting but deleteriously impact charge dissociation/transport/recombination because of the defects existed on the surface and grain boundaries of the perovskite films as well. Here, we demonstrate passivation of the perovskite surface and grain boundaries by small molecules through infiltration of subphthalo-cyanines (SubPc) into the perovskite film. Reduced surface defects have been obtained, which was verified by XRD and time-resolved dynamics measurements. As a result, the power conversion efficiency for the solution-processed planar heterojunction solar cells has been enhanced from 9.96% for the contrastive perovskite solar cells to 13.6% for the SubPc passivated perovskite solar cells.