Depositions and characterization of sol–gel processed Al-doped ZnO (AZO) as transparent conducting oxide (TCO) for solar cell application

Abstract

Al-doped ZnO (AZO) thin films are deposited on glass substrate by sol–gel spin coating using zinc acetate dihydrate as a precursor with different molar concentrations varying from 0.35 to 0.75 mol/L. To investigate the structural, electrical, optical and morphological properties of AZO films, XRD, four-point probes, HE measurement, UV–Vis spectrometry and SEM with EDX are used. Thickness of the thin film is measured by a surface profilometer. The structural characteristics show a hexagonal wurtzite structure with a (002)-preferred orientation. Optical study reveals that transmittance is very high (up to 90%) within the visible region and optical band gap, E_g varies from 3.25 to 3.29 eV with Zn concentration. The carrier concentration increases and resistivity decreases with the increase in Zn concentration. Thin films fabricated with 0.75 mol/L of Zn concentration exhibit the best electrical property. SEM study shows non-uniform surface of the films where EDX confirms the formation of AZO. The results revealed by this study prompt a high interest to use AZO as transparent conductive oxide for advanced applications such as displays, solar cells and optoelectronic devices.