Impact of aluminium doping in magnesium-doped zinc oxide thin films by sputtering for photovoltaic applications

Abstract

In this study, Mg-doped zinc oxide (MZO) thin films were deposited through radio frequency (RF) sputtering for different substrate temperatures ranging from room temperature (25 °C) to 350 °C. XRD analysis depicted that the higher substrate temperatures lead to increased crystallite size. From the UV–Vis spectroscopy, transmittance (T) was found approximately 95% and the optical band energy gap (Eg) was determined around 3.70 eV. Hall effect measurement system measured the carrier concentration and resistivity of all films in the order of 1014 cm−3 and 103 Ω-cm, respectively. Since the structural and optoelectrical properties of the MZO films were not significantly affected by the substrate temperatures, Aluminium (Al) was co-doped in the MZO film to improve structural and optoelectrical properties. As a result, the carrier concentration of Al doped MZO (AMZO) films was increased up to ~ 1020 cm−3 from ~ 1014 cm3 (MZO), and the resistivity was decreased up to ~ 10–1 Ω-cm from 103 Ω-cm (MZO) representing the significant changes in electrical properties without affecting the transmittance. This study opens a pathway for improving the MZO buffer layer that can enhance the cell performance of CdTe solar cells. Graphical abstract