Defect Passivation: Physisorption or Chemisorption? A Nonadiabatic Molecular Dynamics Study

Nonradiative charge recombination, originating from defects, limits the use of semiconductors in solar energy conversion technologies. Defect passivation is an effective approach to eliminating charge recombination centers. Focusing on InSe semiconductor, we have shown that the adsorption configurations of passivators have a strong impact on the defect passivation, using nonadiabatic molecular dynamics combined with time-dependent density functional theory. The simulations demonstrate that the physisorption passivator cannot eliminate the recombination centers, resulting in fast nonradiative charge recombination. By contrast, the chemisorption passivators are able to form covalent bonds with indium, remove the charge recombination centers, thereby prolonging the charge recombination time by more than a factor of 10 because of the decreased nonadiabatic coupling and channels for charge and energy losses. This study uncovers the microscopic effects of the adsorption configurations of passivators on the photogenerated charge carrier dynamics, suggesting that chemisorption passivators are essential for defect passivation.