Uneven Strain Relaxation in Formamidinium Lead Triiodide (FAPbI3) Films upon Aging

Perovskite solar cells (PSCs) typically experience performance degradation over time, which limits their long-term utility. Interestingly, certain observations indicate a self-enhancement phenomenon where device performance improves without external intervention. This study delves into the aging process of perovskite films, examining their structural evolution through advanced microscopic techniques. The findings reveal that aging can induce partial lattice strain relaxation, which enhances photoluminescence, reduces trap density, and increases open-circuit voltage (V-oc). These improvements collectively boost the overall power conversion efficiency (PCE). The study further investigates the effect of additives, specifically methylammonium chloride (MACl), on the aging process. Varying MACl concentrations influence the aging rate, with higher concentrations having more significant effects. Additionally, the research explores methods to expedite aging, achieving a peak PCE of 25.1% by eliminating residual Cl through heat and humidity treatment. This research provides valuable insights into the aging dynamics of PSCs and suggests approaches for rapid self-enhancement, essential for enhancing stability in commercial applications.