Water dopant control of structural stability and charge recombination of perovskite solar cells: A first-principles study

Humidity is a key factor in affecting the long-term stability of perovskite solar cells. However, how water interacts with the perovskite film and influences the individual energy conversion process in perovskite solar cells remains virtually unexplored. By using ab initio molecular dynamics and nonadiabatic molecular dynamics, we reveal that the MAX-terminated surface is more susceptible to water erosion. The intrusion of water brings in severe lattice distortion, whose degree follows the law of MAPbI₃ > MAPbBr₃ > MAPbCl₃, thereby leading to attenuation in optical absorbance. Unexpectedly, the carrier lifetimes of hydrated MAX-terminated systems are prolonged, while the PbX-terminated surfaces are largely unaffected. This is due to the dielectric shielding effect of invading water molecules, hindering electron-hole recombination. Our results shed light on a comprehensive understanding of the complex effect of humidity on the perovskite performance, rationalize the contradictory experimental observations, and provide novel insights for further optimization of renewable energy devices.