Formation and Recombination Dynamics of Polarons in Goethite: A Time-Domain Ab Initio Study

The temperature and the coordination environment significantly affect polaron dynamics. Using goethite (FeOOH) as a model, our study examines polaron formation and recombination behavior under various conditions, including electron injection, photoexcitation, and heterovalent doping. Ab initio and nonadiabatic molecular dynamics (NAMD) simulations reveal that polaron formation in FeOOH is dependent on temperature via an adiabatic mechanism with higher temperatures leading to shorter formation times. Only electron polarons form in FeOOH, regardless of the formation method. NAMD simulations indicate that photoexcited electron polaron recombination is significantly faster in FeOOH than in Fe₂O₃. This difference arises from the distinct coordination environments, resulting in higher inelastic charge-phonon scattering and stronger nonadiabatic coupling in FeOOH. Our findings highlight the crucial roles of temperature and coordination environment in polaron dynamics, offering valuable insights for designing materials to optimize carrier dynamics.