SYNTHESIS AND CHARACTERIZATION OF TIN DOPED CADMIUM OXIDE NANOPARTICLES FOR POTENTIAL USE IN PHOTOVOLTAIC APPLICATIONS

Abstract

There is an increasing need for renewable energy and in particular, photovoltaic cells due to finite resource of fossil fuel and the associated climate change. A future solar -cell needs to be produced in an environmentally friendly way, more efficient and cheaper so as to be sustainable and competitive alternative source of energy. Cadmium oxide (CdO), a semiconductor material in group II -VI is of high transparency, superior optical transmission and low electrical resistivity. This study involved the synthesis and characterization of undoped and tin-doped CdO nanoparticles for photovoltaic applications using a facile sol-gel wet chemical route by controlling the reaction time, pH and tin concentration in the precursor to obtain optimized nanoparticles. This study focuses on the effects of various reaction parameters like reaction time, pH, and precursor concentrations on the material properties of the samples. Morphology and the structure of undoped and tin doped CdO were examined by use of an X-ray diffractometer and scanning electron microscopy techniques respectively. XRD analysis showed Face-centered cubic of CdO with the crystallite size estimated to be ranging from 18.03 to 26.67 nm for the experimental factors. The XRD pattern of undoped and Sn doped CdO nanoparticles matched well with the standard CdO crystal structure with variation in peak intensities observed to be corresponding reference card number JCPDS Card No. 05-064. SEM displayed aggregation of nanoparticles when the precursor pH increased from 7 to 12 which confirms alkaline medium promotes crystallization (structural order) and particle formation or nucleation. The morphological changes caused by varying reaction time were better understood by using SEM imaging, which showed differences in particle size, shape and aggregation patterns. To ascertain the functional groups in the samples, Fourier transform infrared spectroscopy was used. The FTIR spectra displayed a prominent absorption band around 700 cm−1, corresponding to the Cd-O stretching vibration. Presence of OH stretching bands above the 3000 cm-1region indicating surface hydroxylation in all theexperimental factors. The absorbance and transmittance of the nanoparticles was analyzed using UV-Vis spectroscopy with radiations at normal incident to the sample in the range 400 nm to 1200 nm. UV-Vis analysis showed absorption peaks varying from 380 – 376 nm for precursor pH values 7 – 12, with band gap energy range of3.116 – 3.584 eV. The research findings showed optimize results at longer reaction time, pH of 8 and 3% Sn-doping concentration possibly contribute to the development of sustainable and cost-effective photovoltaic devices.