Multifunctional dual-anion compensation of amphoteric glycine hydrochloride enabled highly stable perovskite solar cells with prolonged carrier lifetime

Throughout years, the two-step spin-coating process is the most common method to prepare organic lead halide perovskite materials. However, the short reaction time of dropping the solution at the second step means that PbI₂ cannot be completely transformed into perovskite phase. To solve this problem, we report the introduction of glycine hydrochloride (GlyHCl) into the second step of the two-step spin-coating process to prepare a FA_0.9MA_0.1PbI₃-x%-GlyHCl perovskite material (namely FAMA-x%-GlyHCl, where FA = formamidinium, MA = methylammonium, and x% stands for the molar ratio of GlyHCl added in FA iodide/MA iodide (FAI/MAI) precursor solution). The Cl⁻ ion in GlyHCl assists the formation of α-phase perovskite, and the –COO⁻ group coordinates with Pb²⁺ cation in a bridging way, making up for the anion vacancy in perovskite lattice and resulting in high absorption intensity. The perovskite solar cells (PSCs) based on FAMA-9%-GlyHCl achieve a long carrier lifetime (527.0 ns), a photoelectric conversion efficiency (PCE) of 19.40% and good thermal stability, maintaining 85.8% of the initial PCE after being continuously heated at 60 °C for 500 h. This study helps to solve the problem of incomplete reaction in the two-step spin-coating process and puts forward a new solution for preparing high coverage perovskite films with large grain size.