Potassium iodide reduces the stability of triple-cation perovskite solar cells
Tarek I. Alanazi, Onkar S. Game, Joel A. Smith, Rachel C. Kilbride, Claire Greenland, Rahul Jayaprakash, Kyriacos Georgiou, Nicholas J. Terrill, David G. Lidzey
Abstract
electron transport layers (ETL), we propose that defect passivation using KI is highly sensitive to the composition of the perovskite-ETL interface. We reconfirm findings from previous reports that KI preferentially interacts with bromide ions in mixed-halide perovskites, and - at concentrations >5 mol% in the precursor solution - modifies the primary absorber composition as well as leading to the phase segregation of an undesirable secondary non-perovskite phase (KBr) at high KI concentration. Importantly, by studying both material and device stability under continuous illumination and bias under ambient/high-humidity conditions, we show that this secondary phase becomes a favourable degradation product, and that devices incorporating KI have reduced stability.