Monitoring a Silent Phase Transition in CH₃NH₃PbI₃ Solar Cells via Operando X-ray Diffraction

The relatively modest temperature of the tetragonal-to-cubic phase transition in CH3NH3PbI3 perovskite is likely to occur during real world operation of CH3NH3PbI3 solar cells. In this work, we simultaneously monitor the structural phase transition of the active layer along with solar cell performance as a function of the device operating temperature. The tetragonal to cubic phase transition is observed in the working device to occur reversibly...