Abstract
Investigating the optical response of quantum dots subjected to an external electric field offers key insights into their suitability for nanoelectronic device integration. In this study, we employ first-principles calculations to elucidate the Stark effect in both InP core and InP/ZnSe core/shell quantum dots. Our analysis reveals three characteristic Stark shift behaviors, including quadratic, linear, and hybrid quadratic-linear responses, where each is directly linked to the evolution of the excitonic dipole moment, reflecting the intrinsic electron-hole separation (D (0i) , where i = x, y, z) in the absence of an applied field. Calculated electron densities for excited states demonstrate that spectral energy ΔE increases as |D (i) | decreases under an external electric field, reaching a maximum when |D (i) | approaches zero. For all the QDs examined, D (0x) is approximately zero, so an applied field along the x-direction consistently enlarges |D (x) |, resulting in a red shift. In contrast, the spectral response along the y or z axes depends on the alignment of the field orientation relative to D (0i) : fields aligning with the electron-hole vector enhance separation (red shift), while opposing fields reduce it (blue shift). The magnitude of |D (0i) | is primarily determined by core/shell electronic structure: small-core (InP)(10)(ZnSe)(67) exhibits quasi-type II behavior with large |D (0z) |, while larger-core (InP)(27)(ZnSe)(50) and pure (InP)(77) show type-I-like localization with small |D (0i) |. These findings indicate that the Stark shift characteristics of InP/ZnSe QDs can be tailored by adjusting the thickness of the core or shell layer of QDs.