The Interplay Between Lead Vacancy and Water Rationalizes the Puzzle of Charge Carrier Lifetimes in CH₃NH₃PbI₃: Time‐Domain Ab Initio Analysis

Abstract

The perovskite CH3NH3PbI3 excited‐state lifetimes exhibit conflicting experimental results under humid environments. Using ab initio nonadiabatic (NA) molecular dynamics, we demonstrate that the interplay between lead vacancy and water can rationalize the puzzle. The lead vacancy reduces NA coupling by localizing holes, slowing electron–hole recombination. By creating a deep electron trap state, the coexistence of a neutral lead vacancy and water molecules enhances NA coupling, accelerating charge recombination by a factor of over 3. By eliminating the mid‐gap state by accepting two photoexcited electrons, the negatively charged lead vacancy interacting with water molecules increases the carrier lifetime over 2 times longer than in the pristine system. The simulations rationalize the positive and negative effects of water on the solar cell performance exposure to humidity.

Nuclear Quantum Effects Accelerate Charge Recombination but Boost the Stability of Inorganic Perovskites in Mild Humidity

“…Further study indicates the interplay between the water molecules and lead vacancy in HOIPs significantly accelerates the nonradiative recombination. 15 On the all-inorganic perovskite side, dozens of experiments have also shown that the stability and optoelectronic characteristics of inorganic perovskite solar cells (PSCs) depend on the humidity conditions. Meloni and co-authors demonstrated that exposing the CsPbBr 3 perovskite films to humidity can enhance the crystallinity of films and improve device performance.…”