Structural, optical and thermoelectric properties of Al-doped ZnO thin films prepared by spray pyrolysis

In the present work, pure and Al-doped ZnO thin films were prepared on glass substrate by spray pyrolysis method for different concentration of aluminum (Al). The X-ray diffraction confirms that all deposited ZnO thin films have poly crystalline hexagonal structure and highly oriented along the c-axis, (002) plane. The morphology of the films was investigated by field emission scanning electron microscope (FESEM) and the particle's shape are found to be changed from cashew nuts to hexagonal for doping concentration of 10 wt%. The optical band gap (E-g) and lattice strain (epsilon) of ZnO thin films are found to be decreased, while the value of Seebeck coefficient (S) is increased with increase of Al doping concentration. The maximum value of Seebeck coefficient (-56 mu V/K) has been achieved at 300 K for 10 wt% Al-doped ZnO thin films. As-prepared Al-doped ZnO thin films with their high Seebeck coefficients and low band gap can be used for thermoelectric and optoelectronic devices applications.