ZnO Vacancy Homojunction for Phonon-Enhanced Directional Charge Transfer

Abstract Directional charge transport is essential for efficient photocatalysis, yet carrier transfer in semiconductor nanocrystals is often random and limited by recombination. Although electron−phonon coupling strongly influences carrier dynamics, phonons are more commonly associated with energy dissipation than with enhanced charge transport. Here, we construct a ZnO vacancy homojunction composed of donor-type oxygen vacancies and acceptor-type zinc vacancies, establishing an intrinsic pathway for directional charge transfer. The resulting n−p junction introduces both an internal electric field and asymmetric lattice distortion, enabling phonon-assisted directional carrier transport under ultrasonication and leading to significantly enhanced photocatalytic performance in methylene blue degradation compared with conventional ZnO. Combined spectroscopic measurements, radical-trapping experiments, and density functional theory calculations reveal a phonon-enhanced directional charge-transfer mechanism. These findings provide a general strategy for regulating directional charge transport through lattice dynamics.