Large grain size with reduced non-radiative recombination in potassium incorporated methylammonium-free perovskite solar cells

Organic–inorganic hybrid halide perovskites are widely considered to be one the most promising material in photovoltaic technology, the use of this semiconductor as absorbent layer in solar cells has attracted considerable interest due to their excellent properties. It has been reported that the incorporation of potassium ion is a powerful strategy to tune the perovskites properties, notwithstanding there has been some disagreement regarding the role of this monovalent alkali metal within the perovskite structure. Here, we investigated the impact of K+ on the film properties and photovoltaic performance in double cation perovskite solar cells Cs0.1FA0.9PbI3. Our results show that K+ intervenes in the crystallization process inducing the extraction of non-reactive PbI2 from the bulk, resulting in a notable enhancement in morphology and reduced non-radiative recombination. The solar cells fabricated with 3% of K+ content achieve a PCE of 19.3%, showing a significative improvement in Jsc, Voc and stability values compared with control devices.