Optical band gap engineering of ZnO nanophosphors via Cu incorporation for ultraviolet–violet LED

Abstract

The tunability of optical band gap and augmentation of luminescence intensity of Cu-doped ZnO nanophosphors for ultraviolet and violet light-emitting diodes grown by microwave-assisted aqueous solution technique were studied at room temperature for various doping concentrations. The UV–Vis spectral analysis demonstrated that band gap engineering of ZnO nanophosphors can be performed through incorporation of Cu ions into the ZnO matrix by controlling the dopant content. The photoluminescence investigations revealed that a strong UV emission centred around 346–348 nm and an intense violet band comprising of two peaks centred about 403 nm and 424 nm occur in the absence of any other band. A thorough study of the defect-related PL spectra elucidated that these violet peaks originated from energetically more probable deep-acceptor zinc vacancy and shallow-donor zinc interstitial defect transitions. The luminescence intensity of nanophosphors can be optimized through modification of intrinsic defect density by adjusting Cu concentration in the ZnO host. The results are significant for ZnO-based photoluminescence cutting-edge technology.