Synthesis and Characterization of Zinc Oxide (ZnO) Thin Films for Solar Cell Applications Using Sol-Gel Auto Combustion Technique

Abstract

Zinc oxide (ZnO) nano particles were prepared using sol-gel auto combustion method from Zinc acetate dehydrate and sodium hydroxide. Their structural, morphological, optical and electrical properties were studied. X-ray diffraction (XRD) analysis revealed the film’s hexagonal wurtzite phase with preferred (101) grain orientation. The mean crystallite size calculated using the Debye-Scherrer model was 23nm with lattice parameters a=0.3255nm and c=0.5185nm (CF. JCPDS 361451) and small dislocation density of 1.8 x 10-3nm-2, which shows the presence of few lattice defects and very good crystallinity. Scanning electron microscope (SEM) micrographs revealed the film granular porous structure composed of collections of hexagonal columnar grains in a direction normal to the substrate surface and an average grain size of around 198.86nm. The UV-Vis room temperature optical absorption coefficient was analysed using the transmission spectra data and the optical band gap energy was estimated to be around 3.3eV. A low electrical resistivity value of 2.35x10-4Ωm was obtained and a high value of carrier charge mobility was found to be 185cmV-1S-1. The results of this work are important for applications in semiconductor devices particularly solar cells, optical sources and detectors.