Enhancement of Perovskite Solar-Cell Efficiency Using FAPbBr(3)/I-3 with Methylammonium Chloride

Abstract

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 alpha-phase FAPbI3 film due to the relatively easy formation of the more stable 5-FAPbI(3) (hexagonal structure). To overcome this, in this study, formamidinium lead bromide (FAPbBr(3)) was used to induce the synthesis of stable alpha-phase FAPbI(3). The resulting light-absorbing layer was composed of (FAPbI(3))(0.95)(FAPbBr(3))(0.05), but 5-phase FAPbI(3) could be still observed. To suppress the formation of delta-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%.