Study on Electrical, Optical Properties of ZnSe/SiO2 Composite Thin Film Using Sol-Gel Dip Coating Techniques

Abstract

This study seeks to obtain data about electric and optical properties of ZnSe/SiO2 composite films for Photovoltaic Applications, for this purpose ZnSe nanoparticles established in [Si O2] thin films were prepared by sol-gel method using zinc acetate dihydrate [Zn (CH3 COO)2 .2H2O], selenic acid [H2SeO4] and Tetraethyl orthosilicate [Si(OC2H5)4]. The n – ZnSe /SiO2 thin film composites were deposited on the glass substrate by dip coating technique. Mobility activation has been studied from the photocurrent degradation curves. XRD results indicate the phase structure of ZnSe particles embedded in ZnSe/SiO2 composite thin films is sphalerite (cubic ZnS). The effective density of states (Neff), frequency factor (S), and trap depth (E) have been calculated for all the films having different crystallite sizes. The increase in photoconductivity is explained in terms of built in potential barriers (φb) at the crystallite boundaries. Field Emission Scanning Electron Microscopy (FESEM) image show that morphology of n - ZnSe influenced by ZnSe/SiO2 molar ratio. The optical characterization of thin film composite has been examined by transmittance measurement in the UV-visible wavelength range. It was found that the optical transmission is decreased with increase of the ZnSe/SiO2 molar ratio.  The highest transmission of 54.6% and the lowest of 36.7% were acquired for the specimens with 5% and 20% ZnSe/SiO2 molar ratio, respectively.  Further observation shows that the optical transition in ZnSe/SiO2 thin film is direct transition with band gap energy in the range of 2.6 - 3.9 eV.