Influence of the mixed organic cation ratio in lead iodide based perovskite on the performance of solar cells.

Lead halide based perovskite solar cells are presently the flagship among the third generation solution-processed photovoltaic technologies. The organic cation part in the perovskite plays an important role in terms of crystal structure tuning from tetragonal to trigonal or pseudocubic or vice versa depending on the organic cations used, while it also displays different microstructure. In this paper, we demonstrate the influence of the organic cation part with respect to optical properties, hysteresis behavior, and stability. This study offers a clear understanding of the perovskite properties and how they can be modulated by compositional engineering. With a rational choice, light harvesting abilities and hysteresis behavior can be controlled in these systems. The substitution of formamidinium cation by methylammonium cation allows achieving low temperature annealing and inducing stability in perovskites together with enhanced photovoltaic properties. By the use of in-situ scanning force microscopy experiments the conversion of precursors to perovskite at a particular temperature can be visualized.