Boosting optoelectronic performance of (FA)X(MA)1-XPbI3 perovskite solar cells: Via FAI post-treatment engineering

Complex composition engineering of mixed-cations perovskite (FAxMA1-xPbI3) has recently supported rapid progress in perovskite solar cells (PSCs). Nevertheless, it is insufficient to embed and accommodate formamidinium (FA) cation into the MAPbI3 lattice structure via existing methods, leaving behind masses of FA or lead halide content and deteriorating photovoltaic performance. Herein, we present facile surface engineering via post-treated methodology, the surface of CH3NH3PbI3 (MAPbI3) films post-treated with formamidinium iodide (FAI) solution and that results get mixed-cation FAxMA1-xPbI3 perovskite films. The mixed-cation-based FAXMA1-XPbI3 perovskite with significant and large grain size, uniform and compact morphology highly crystallization, and consequently reducing defect density of the perovskite films can be produced via the present method. It is observed that the film, post-treated with FAI-2, shows results in a very stable and highly crystalline lattice structure with attributes such as extended carrier lifetime, better electron transport, and decreased defect density. The optimized device demonstrates a promising power conversion efficiency (PCE) of 21.89%, and higher than that of the non-treated (19.08%) devices. Furthermore, the devices based on the novel FAI-post-treatment engineering exhibit significantly enhanced stability compared to non-treated devices. Therefore, this approach provides a novel methodology that offers a simple method for producing superior mixed perovskite films, potentially paving the way for the future exploitation of the boosted performance of perovskite solar cells.