Stable and High-Efficiency Perovskite Solar Cells Using Effective Additive Ytterbium Fluoride.

With better light utilization, larger tolerance factor, and higher power conversion efficiency (PCE), the HC(NH ) (FA)-based perovskite is proven superior to the popular CH NH (MA)- and Cs-based halide perovskites in solar cell applications. Unfortunately, limited by intrinsic defects within the FA-based perovskite films, the perovskite films can be easily transformed into a yellow δ-phase at room temperature in the fabrication process, a troublesome challenge for its further development. Here, ytterbium fluoride (YbF ) is introduced into the perovskite precursor for three objectives. First of all, the partial substitution of Yb for Pb in the perovskite lattice increases the tolerance factor of the perovskite lattice and facilitates the formation of the α phase. Second, YbF and DMSO in the solvent form a Lewis acid complex YbF ·DMSO, which can passivate the perovskite film, reduce defects, and improve device stability. Consequently, the YbF modified Perovskite solar cell exhibits a champion conversion efficiency of 24.53% and still maintains 90% of its initial efficiency after 60 days of air exposure under 30% relative humidity.