Enhancement of Perovskite Solar-Cell Efficiency Using FAPbBr3/I3 with Methylammonium Chloride

Organic/inorganic metal halide formamidinium lead iodide (FAPbI 3 ) perovskites exhibit excellent optical properties, a suitable band gap, a wide light-absorption range, and superior electron-hole mobility. However, it is difficult to fabricate high-quality α-phase FAPbI 3 film due to the relatively easy formation of the more stable δ-FAPbI 3 (hexagonal structure). To overcome this, in this study, formamidinium lead bromide (FAPbBr 3 ) was used to induce the synthesis of stable α-phase FAPbI 3 . The resulting light-absorbing layer was composed of (FAPbI 3 ) 0.95 (FAPbBr 3 ) 0.05 , but δ-phase FAPbI 3 could be still observed. To suppress the formation of δ-phase FAPbI 3 , methylammonium chloride (MACl) was added to the (FAPbI 3 ) 0.95 (FAPbBr 3 ) 0.05 precursor solution. At an optimal MACl content of 40 mol%, perovskites with improved crystallinity and large crystallite size could be fabricated, resulting in a perovskite solar-cell efficiency of 18.204%.