Investigation on the effect of Al concentration on the structural, optical and electrical properties of spin coated Al:ZnO thin films

Al doped ZnO thin films were deposited using sol-gel spin coating method onto ITO coated glass substrate and their structural, optical and electrical properties were investigated through XRD, UV-Visible spectroscopy and two probe set up, respectively. Structural studies reveal that, undoped films are polycrystalline in nature where as Al doping show significant preferred orientation along c - axis. Optical studies reveal >90% transparency in films and also an increase in the band gap energy with Al doping, due to increase in the carrier concentration of the Al doped ZnO and the mechanism is well explained on the basis of Burstein - Moss effect. In addition, Urbach energy was estimated and found to increase with increase of Al content, indicating decrease in the defect density of the films, in supportive with the XRD results. Also, sheet resistance of Al doped ZnO films found to decrease with increase in Al concentration. The investigated results confirm that Al doped ZnO films are feasible and potential candidates for TCO applications.