Defect Passivation:\nPhysisorption or Chemisorption?\nA Nonadiabatic Molecular Dynamics Study

Nonradiative charge recombination, originating from defects,\nlimits\nthe use of semiconductors in solar energy conversion technologies.\nDefect passivation is an effective approach to eliminating charge\nrecombination centers. Focusing on InSe semiconductor, we have shown\nthat the adsorption configurations of passivators have a strong impact\non the defect passivation, using nonadiabatic molecular dynamics combined\nwith time-dependent density functional theory. The simulations demonstrate\nthat the physisorption passivator cannot eliminate the recombination\ncenters, resulting in fast nonradiative charge recombination. By\ncontrast, the chemisorption passivators are able to form covalent\nbonds with indium, remove the charge recombination centers, thereby\nprolonging the charge recombination time by more than a factor of\n10 because of the decreased nonadiabatic coupling and channels for\ncharge and energy losses. This study uncovers the microscopic effects\nof the adsorption configurations of passivators on the photogenerated\ncharge carrier dynamics, suggesting that chemisorption passivators\nare essential for defect passivation.