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.

Automated summary

This study explores the stability of an uncharted mixed perovskite material optimized for low-temperature processable device architectures. The system showed remarkable stability under certain conditions but was jeopardized under more severe aging conditions. Advanced characterization techniques helped identify the degradation mechanisms and revealed an unexpected protective effect of gold electrodes.