Effects of Al-dopant concentration on the thermoelectric power factor of ZnO films prepared by spray pyrolysis deposition

Abstract

Semiconductor doping is the intentional introduction of impurities into an intrinsic semiconductor to control its properties. In this study, the effects of varying aluminum (Al) dopant concentration on the thermoelectric power factor, including Seebeck coefficient and electrical conductivity, of zinc oxide (ZnO) films were investigated. The films were fabricated using spray pyrolysis deposition followed by a post-annealing treatment. The films were characterized based on their structural properties using X-ray diffraction (XRD) analysis and their optical properties using UV-Visible (UV-Vis) spectroscopy. The Seebeck coefficient of the films was measured using a custom-made setup while the electrical conductivity was determined using the Van der Pauw method at room temperature. The XRD analysis, indicating decreasing lattice parameters and crystallite size, confirms the hexagonal wurtzite structure of the ZnO films and successful doping by Al substitution. The UV-Vis spectra, utilizing Tauc plot approximation, reveal a decreasing band gap energy with increasing doping levels. The measured Seebeck coefficients increase with doping concentration while the electrical conductivity is maximum at 2% Al-dopant concentration. The findings in this study suggests that Al-doping on ZnO enhances the thermoelectric power factor under optimized doping concentration.