Synergistic effect of potassium and iodine from potassium triiodide complex additive on gas-quenched perovskite solar cells

Gas-quenching has been demonstrated to be a robust and reliable method for fabricating perovskite solar cell (PSCs) and is a technique for large area and large-scale production. Although additive engineering has been used to improve various perovskite fabrication methods, it is yet to be utilised by gas-quenching. Herein, we introduce potassium triiodide complex (KI3) as a novel additive to the perovskite precursor solution for gas-quenched PSCs. The resultant perovskite film exhibits broader spectral response, enhanced photoluminescence and prolonged carrier lifetime, due to halide exchange and defect passivation brought about by the I-2 supplied by the KI3 complex. The champion device fabricated from precursor with mixed KI and KI3 additives delivered a steady-state power conversion efficiency of 21.2% with negligible hysteresis due to the presence of potassium salt. This efficiency is the highest for PSCs fabricated by gas-quenching. Moreover, the KI3 additive has substantially improved the stability of the precursor solution, allowing high performance devices to be fabricated with aged solution, which widens the process window for perovskite film deposition and lengthens the lifetime of precursors which are important prerequisites for large scale production of PSC.