Optical Band Gap Tailoring and Enhanced Electrical Performance of Cu-Doped ZnO Thin Films via Sol-Gel Fabrication

Abstract

Copper-doped zinc oxide (CZO) thin films have been widely investigated owing to their potential application in optoelectronic devices. In this study, we report the optical and electrical properties of zinc oxide (ZO) and copper-doped zinc oxide (CZO) thin films prepared using the sol-gel method. The copper concentration was changed to investigate the impact of copper doping on the optical and electrical properties of the films.  The absorption spectra revealed that copper doping caused the absorption edge to redshift, which triggered ZO's bandgap energy to increase from 3.16 eV to 3.47 eV. Electrical measurements calculated the electrical resistivity of the thin films. For ZO and CZO, copper doping resulted in a decrease in resistivity from 2.272 W-cm to 0.904 W-cm and an increase in carrier concentration. This property can be useful in some conditions, where low resistivity and high conductivity are required, such as transparent conductive coatings for optoelectronic devices. The optical analysis shows how the film's Urbach energy increases with the rise in Cu doping percentage.

Dhaka Univ. J. Sci. 74(1): 111-121, 2026 (January)