Interpreting Accelerated Tests on Perovskite Modules: Using Photooxidation of MAPbI3 as an Example

Solar panels based on metal halide perovskites are following a fast track to commercialization. However, unlike more established solar cell types, there are not yet decades-long field observations to increase consumer confidence. Thus, one must rely heavily on accelerated stress tests to demonstrate reliability. This work uses published experimental data for O2 diffusion and dry photooxidation of methylammonium-lead-iodide (MAPbI3) to estimate the acceleration factors (AF') of some common module accelerated tests. AF' are found to be low. These tests are thus only useful to screen for early failures. Commonly used dark damp heat will accelerate hydrothermal degradation but will not produce relevant photooxidative degradation. Module design choices affect degradation rate. Some degradation mechanisms may cause power loss at lower gas concentrations than dry photooxidation. For photooxidation of MAPbI3, diffusion of O2 into the package limits the degradation rate, allowing a simpler calculation. Steps for predicting decades of performance behavior without decades of field observation are presented.