title: Moderate Humidity Delays Electron-Hole Recombination in Hybrid Organic-Inorganic Perovskites: Time-Domain Ab Initio Simulations Rationalize Experiments.
abstract: Experiments show both positive and negative changes in performance of hybrid organic-inorganic perovskite solar cells upon exposure to moisture. Ab initio nonadiabatic molecular dynamics reveals the influence of humidity on nonradiative electron-hole recombination. In small amounts, water molecules perturb perovskite surface and localize photoexcited electron close to the surface. Importantly, deep electron traps are avoided. The electron-hole overlap decreases, and the excited state lifetime increases. In large amounts, water forms stable hydrogen-bonded networks, has a higher barrier to enter perovskite, and produces little impact on charge localization. At the same time, by contributing high frequency polar vibrations, water molecules increase nonadiabatic coupling and accelerate recombination. In general, short coherence between electron and hole benefits photovoltaic response of the perovskites. The calculated recombination time scales show excellent agreement with experiment. The time-domain atomistic simulations reveal the microscopic effects of humidity on perovskite excited-state lifetimes and rationalize the conflicting experimental observations.
authors.affiliation: College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing 100875, P. R. China.|School of Physics, Complex & Adaptive Systems Lab, University College Dublin , Belfield, Dublin 4, Ireland.
authors.forename: Run
authors.initials: R
authors.lastname: Long
authors.affiliation: College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Weihai
authors.initials: W
authors.lastname: Fang
authors.affiliation: Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States.
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Prezhdo