LAUSR

A small amount of a radical-bearing redox-active polymer, poly(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl methacrylate) (PTMA), incorporated into the photovoltaic organo-lead halide perovskite layer significantly enhanced durability of both the perovskite layer and its solar cell even exposure to ambient air or oxygen. The radical PTMA polymer acted as an eliminating agent of the superoxide anion radical formed upon light-irradiation on the layer, which can react with the perovskite compound and decompose it to lead halide. A cell fabricated with the PTMA-incorporated perovskite layer and a hole-transporting polytriarylamine layer gave a photovoltaic conversion efficiency of 18.8% (18.2% for the control without PTMA). The photovoltaic current was not reduced in the presence of PTMA in the perovskite layer probably owing to a carrier conductivity of PTMA. The incorporated PTMA also worked as a water-repelling coating for providing humidity-resistance to the organo-lead halide perovskite layer.