Transparent self-powered ZnVO2/CdGa 2O3 heterostructure for integrating UV photodetection and luminescent down-conversion

Abstract

The coupling of light detection, emission, and transmission, along with self-powering in a single optoelectronic chip, is required for next-generation, energy-efficient devices, yet remains severely challenging. Here, Zn-doped VO₂ (ZnVO₂) nanowire networks are grown on Cd-doped Ga₂O₃ (CdGa₂O₃) thin films to fabricate a transparent self-powered ZnVO₂/CdGa₂O₃ heterostructure, which simultaneously enables ultraviolet (UV) photodetection and luminescence down-conversion under a single excitation source. Individually, Cd doping in Ga₂O₃ destabilizes the characteristic self-trapped hole-associated UV emission and produces a broad green luminescence band resulting from Cd-induced defect state, while Zn-doping introduces oxygen vacancies, stimulating the green luminescence in ZnVO₂ along with the characteristic UV and yellow emissions originating from distinct recombination channels within its correlated electronic configuration. The heterostructure fabricated from ZnVO₂ nanowire and CdGa₂O₃ film exhibits semiconductor diode-like rectifying characteristics and functions as a self-powered ultraviolet photodetector with a high sensitivity of 251 mA/W and a fast response time of 85 ms. The built-in field at the heterostructure interface promotes effective charge-carrier segregation and recombination under zero bias, producing bright orange-red luminescence visible to the naked eye when the device functions as a self-powered UV photodetector. In particular, this integrated device maintains ~75% transparency and provides a clear view through the device architecture. This photodetector heterostructure absorbs 5-3 eV high-energy broadband UV light and converts it into low-energy orange-red luminescence covering 2.2-1.51 eV, reflecting efficient luminescent down-conversion. The coupling of broadband UV detection, visible-light emission, optical transparency, and self-powered operation into ZnVO₂/CdGa₂O₃ heterostructure makes it suitable for integrated photonics, photovoltaic windows, flexible display technologies, and luminescent down-conversion electrodes for photovoltaics.