Degradation Mechanisms in a Mixed Cations and Anions Perovskite Solar Cell: Mitigation Effect of the Gold Electrode

The stability of an uncharted FA(0.9)5Cs(0.05)Pb-(I0.83Br0.17) 3 mixed perovskite optimized for a low-temperature processable device architecture is explored. The gold electrode was found to generate a safeguard mechanism. Both electron- and hole-transporting layers, respectively, made of SnO2 nanoparticles and a doped poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] polymer were selected for their compatibility with solution processes and good final transparency. This allows a large range of possible applications. Three aging conditions were chosen to decorrelate the effects of temperature, oxygen, and humidity. A remarkable stability of the system was evidenced with, for instance, a low power conversion efficiency loss below 25% after 500 h at 85 degrees C in the dark. This stability was however jeopardized with more severe aging conditions. An in-depth study with microstructural, optical, optoelectronic characterizations, combined with advanced imaging techniques, allowed to identify the degradation mechanisms. We also showed that the perovskite experienced a spatial distribution in the degradation intensity. This could be attributed to an unanticipated protective effect of gold electrodes. The latter could develop a complex with the corrosive tert-butylpyridine doping agent, preventing its diffusion and detrimental consequences on the entire setup.