Quantitative Doping of Chlorine in Formamidinium Lead Trihalide (FAPbI3-xClx) for Planar Heterojunction Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells (PSC) have fascinated remarkable attention owing to the outstanding optical and electronic properties of organic amine lead halide perovskite materials. A one-step approach for the preparation of formamidinium lead iodide (FAPbI3-xClx) perovskite active layer with quantitatively doping of Cl by the reaction of PbI2 FAI FACl and MACl with ratios of 1:(1-x):x:1 at 100°C was developed. A controllable chlorine doping strategy was defined to make the FAPbI3-xClx perovskite film by partially replacing FACl for FAI in the FAPBI3 precursor solution. In this process MACl was as transitional “stabilizer” to preserve the crystal structure for forming the black FA perovskite while the releasing of MACl at 100°C could prevent the escape of FA from the FA perovskite structure. As a result a better device performance was achieved for the 20% FAI being instead by FACl which was due to the enhancement in open-circuit voltage without unnoticeable sacrificing the short-circuit current and fill factor. It is expected that even greater performance enhancement can be achieved through further rational design of halogen doping method.