Resolving the Puzzle of Charge Carrier Lifetime in ZnO by Revisiting the Role of Oxygen Vacancy.

Zinc oxide (ZnO) is a wide bandgap prototypical n-type semiconductor due to the presence of intrinsic oxygen vacancies (V O ). The V O can readily transfer to the most energetically favorable +2 charged V O (V O 2+ ) by losing two electrons mediated by the metastable V O 1+ defect. Nevertheless, the influence of charged V O on the charge dynamics in ZnO and the underlying mechanisms remain elusive. By performing nonadiabatic molecular dynamics simulations of the charge trapping and recombination processes, we show that both V O 1+ and V O 2+ slow down the nonradiative electron-hole recombination via assisted defect states and, thus, extending charge carrier lifetime compared to pristine ZnO. Our study contributes to identifying the different recombination pathways that take place in V O 1+ and V O 2+ of n-type ZnO systems, providing useful guidance for designing high-performance ZnO-based devices.