Multi-band visible photoresponse study of Co2+ doped ZnO nanoparticles

Abstract

In this article, near UV (NUV) and near UV-visible photodetectors (PDs) were fabricated using pure (ZnO) and Co doped ZnO (Zn_1−xCo_xO) nanoparticles synthesised by co-precipitation method. The structural, morphological, compositional and chemical state analysis of the nanoparticles were done using X-ray diffractometry, transmission electron microscopy, energy dispersive spectrometry and X-ray photoelectron spectrometry respectively. The optical spectra which were recorded using a UV-Vis spectrometer exhibited the presence of absorption peaks in the visible region for Co doped ZnO due to d–d transitions. Enhanced photoresponse in the NUV region was found in lower doping concentrations and all the Co doped ZnO photodetectors showed a noticeable response to visible light sources. A maximum responsivity of 63 mA W⁻¹ and quantum efficiency of ∼20% was achieved in the NUV region for the PD fabricated with 2 at% Co doping. The 2 at% Co doped ZnO based photodetector showed efficiency in the range 11–35% for the wavelengths from 401 to 634 nm.