Impact of the Hole-Transport Layer on the Thermal Stability of Inverted Perovskite Solar Cells: An Operando X-ray Scattering Study

The rapid advancement of perovskite solar cells has produced devices with excellent power conversion efficiencies; they are now comparable to those of silicon-based technology. Where perovskite solar cells still lag behind their silicon counterparts is in device lifetime. The various instabilities of lead halide perovskites make understanding device failure mechanisms a very complex─but extremely important─task, and one of the most fundamental environmental stressors for a solar panel is heat. Here, we use thermal operando X-ray scattering experiments, combined with the ISOS-L-2 and L-1 test protocols, to determine how thermally induced changes in the perovskite crystal structure affect device performance. We demonstrate that the stability of the device is influenced not just by the perovskite but also by the choice of hole transport and electrode materials. Electrical bias is identified as an aggravating factor in the thermal degradation pathway. By identifying weak links in the device architecture, we highlight key targets for future work in the improvement of device lifetimes.