Improved Ambient Stability of Inorganic Perovskite Films Through Reduction of Tensile Stress

Samantha Kaczaral1, Gabriel McAndrews1, Boyu Guo2, Aram Amassian2, Rebecca Belisle3, Michael D. McGehee1 1University of Colorado, Boulder, Boulder, CO, United States /2North Carolina State University, Raleigh, NC, United States /3Wellesley College, Wellesley, MA, United States

Understanding degradation mechanisms is crucial to preventing efficiency loss in metal halide perovskite solar cells.  Investigation of degradation caused by tensile stress reveals mixed organic-inorganic perovskite thin films uptake water and oxygen to relieve residual tension. Mass uptake in perovskite films is evident in ambient conditions but not in films held under inert conditions, thus confirming the contribution of water and oxygen in air. Therefore, reduction of residual tension in notoriously moisture sensitive inorganic perovskites should decrease the rate of water uptake in films stored in ambient conditions. By utilizing a diethyl ether antisolvent bath to lower tensile stress, the ambient stability of CsPbI2Br was substantially improved.