Transparent Co3O4/ZnO photovoltaic broadband photodetector

Abstract

Based on the requirements of transparent optoelectronic devices, herein we report a highly transparent broadband photodetector, which is based on spinel structured p-Co3O4 and n-ZnO heterojunction. The XRD and XPS analysis confirmed the wurtzite ZnO phase along with the formation of spinel structured Co3O4. The structural property shows the good crystalline properties of the heterostructure thin films. The optical properties reveal the dual absorption states of Co3O4 corresponding to the Co2+ state (Eg = 1.93 eV) and Co3+ state (Eg = 1.42 eV) along with wide band gap ZnO (3.2 eV). Moreover, the photodetector shows an impressive transmittance of ~76% in the visible window. Further, the photoelectrical performance shows the prominent photovoltaic effect (self-powered operation) with a significant photosensitivity of 4.57 × 104. Moreover, the device is also capable of absorbing broad wavelengths from ultraviolet (UV) to infrared (IR) range. Importantly the device exhibits a fast response speed of 81.7 μs and a decay time of 178.8 μs which are found to be the fastest speed reported for transparent metal oxide-based p-n heterojunction devices under white light and self-powered mode. This work thus provides a comprehensive way of utilizing the robust metal oxide layers for developing a fast-high performing transparent self-powered device. The dual bandgap configuration of spinel Co3O4 demonstrates the wide range photo-responses, which is a promising feature for broadband transparent photodetectors and enhanced transparent photovoltaics.