Defect‐Cascades‐Induced Photodegradation in InP/ZnSe/ZnS Quantum Dots

Abstract By integrating light‐induced in situ electron spin resonance (ESR) spectroscopy with density functional theory (DFT) calculations, it is revealed that surface sulfur vacancies (s‐V _S ) in InP/ZnSe/ZnS quantum dots (QDs) act as critical initiation centers for cascade defect formation, directly compromising photostability and optoelectronic performance of QDs. Blue‐light irradiation initiates defect propagation from s‐V _S , inducing sequential formation of Zn, S, and Se vacancies that extend toward the ZnSe/ZnS interface. This defect cascade disrupts the entire band alignment, shifting it from type‐I to type‐II and drastically reducing external quantum efficiency (EQE). By contrast, the targeted passivation of s‐V _S sites effectively suppresses defect evolution, thereby enhancing photostability and preserving high EQE under prolonged illumination. These findings establish s‐V _S as a principal accelerator of light‐induced degradation, underscoring the necessity of surface defect control for developing highly stable and high‐performance QDs.