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

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 (E_g) 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: (Figure presented.)