Microstructural and optical properties of nanostructured al/Ag co-doped ZnO thin films (AgxAl0.03ZnO0.97-x) by spray pyrolysis for optoelectronic applications

Al/Ag co-doped ZnO (AgxAl0.03ZnO0.97-x, x = 0, 0.02, 0.04, 0.06, 0.08) thin films were prepared using a facile spray pyrolysis deposition route, and their microstructural and optical properties were investigated. Dislocation density reduced and film crystallinity improved with increasing Ag content. This correlated with strain relaxation (∼10−4) and crystallite size enlargement (>23 nm) at high Ag concentrations, as determined by the Scherrer, Williamson-Hall, Halder-Wagner, and Wagner-Agua approximations. The small Urbach energy (<321 meV) and narrow band gap (∼3 eV) observed at low Ag concentration (4 at.%) indicate less structural defects and disorder, and facilitate exciton dissociation with minimum recombination, respectively. The Moss, Herve and Vandamme, and the Ravindra and Gupta models exhibited high correlation between refractive index values (2.09–2.35). Thus, this study demonstrates the enormous potential of Al/Ag co-doping to advance the properties of ZnO films to suit the fabrication of optoelectronic devices, and create opportunities for commercialization.