Preparation of efficient all-inorganic perovskite solar cells from large grain via 1-heptanamine stabilised CsPbI2Br nanoparticles with NH4SCN additive

CsPbI 2 Br is a potential material for perovskite solar cells (PSCs) due to its better thermal stability and high efficiency. Centrifugal deposition for film formation greatly simplifies the steps of the conventional anti-solvent spin coating method, but there are still problems hindering progress, such as small grain size and poor photoelectric performance. In this work, NH 4 SCN was introduced as an additive during the preparation of heptylamine (C 7 H 17 N) stabilised CsPbI 2 Br nanoparticles (NCs) and the films were prepared by centrifugal deposition. The results show that the low melting temperature compounds which formed by thiourea from NH 4 SCN decomposition during annealing and unreacted PbX 2 would link the small grains together by melting and flowing; after PbX 2 precipitation and reaction with CsX, the grain size was significantly increased by about 95 % compared to that of the untreated film. Due to large grains, less defects and high crystallinity, the final power conversion efficiency and fill factor reached 12.25 % and 0.70, respectively.