Improving the performance of perovskite solar cells by surface passivation

NiO has a perfect-aligned energy level with CH3NH3PbI3 perovskite such that it serves as a hole transport layer (HTL), but NiO-based perovskite solar cells (PSCs) still suffer from low efficiency due to the poor interface contact between the perovskite layer and the NiO HTL, and haphazardly stacked perovskite grains. Herein, poly[(9,9 -dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)] (PFBT) is introduced between the NiO and perovskite layers in the form of a polymer aggregate to enhance perovskite crystallinity and decrease the interface charge recombination between perovskite and NiO in PSCs, resulting in an improved performance. Moreover, PFBT modified perovskite films showed sharper, smoother, and more compact crystalline grains with fewer grain boundaries, leading to the decreased nonradiative recombination. This study offers a simple strategy to achieve highly efficient PSCs with the incorporation of polymer semiconductor aggregates to passivate the interface between the perovskite and NiO layers. (C) 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.