We used sol-gel via spin-coating technique to prepare zinc oxide (ZnO) thin films on glass substrates under three different conditions. SEM/EDX and UV-Vis-NIR spectroscopy characterizations were used to analyze the as-grown samples. The surface of all the films is homogeneous, has regular elongated grains and the thin films prepared consist of zinc and oxygen elements. In the wavelength region 200-800 nm, all the samples show high transparency (> 90%). The optical band gap values of the three corresponding ZnO layers were 3.2884, 3.3322 and 3.2985 eV respectively at 0.55 M, 0.75M and 0.95 M conditions and the refractive index values are ranging from 1.982 to 2.009. These properties obtained of the ZnO thin films prepared were examined depending on the precursor concentration conditions and are attractive for use in photovoltaic applications as a buffer layer in copper indium gallium di-selenide (Cu(In,Ga)Se2) solar cells.
Keywords: Spin-coating, ZnO, Band gap, Refractive index.