Mechanistic understanding of the effect bulk defects have on carrier dynamics at the quantum level is crucial to suppress associated midgap mediated charge recombination in semiconductors yet many questions remain unexplored. Here, by employing ab initio quantum dynamics simulation and taking BiVO4 with oxygen vacancies (Ov) as a model system we demonstrate a spin protection mechanism for suppressed charge recombination. The carrier lifetime is significantly improved in the high spin defect system. The lifetime can be optimized by tuning the Ov concentration to minimize the nonradiative relaxation. Our work addresses literature ambiguities and contradictions about the role of bulk Ov in charge recombination and provides a route for defect engineering of semiconductors with enhanced carrier dynamics.
Keywords: Carrier lifetime; ab initio quantum dynamics; bismuth vanadate; nonadiabatic coupling; oxygen vacancy; spin protection.