SYNTHESIS AND CHARACTERIZATION OF TIN-DOPED CADMIUM OXIDE NANOPARTICLES FOR SOLAR CELL APPLICATION

Abstract

The rising demand for clean, sustainable energy globally has led researchers to research on possible improvements on existing materials in photovoltaic applications. Cadmium oxide (CdO), an n-type semiconductor, containing a large bandgap, has the prospective features for solar cell application because of its high visible band transparency, electroconductivity, and stability. This work aimed at synthesizing and characterizing tin (Sn)-doped CdO nanoparticles (CdO: Sn NPs) using wet chemical process at varying ratios of mercaptopropionic acid (MPA), tin (Sn) doping concentration and different calcination temperatures to investigate the effects on the structural and optical properties. X-ray diffraction (XRD) analysis ascertained the retention of the face-centred cubic structure of CdO, indicating the successful incorporation of Sn. Increase in calcination temperature brought enhancement in the Crystallinity, where the optimum crystallite size was 27.98nm at 500 °C. The best optical and structural properties were, however, realized at a calcination temperature of 350°C, after which defect density and agglomeration of the particles became high. The ratio of MPA capping was significant in the customization of nanoparticles. The ratios of 2 ml MPA enabled the crystals to be grown as well-defined and with low defects, giving a low ratio of strain and dislocations, whereas the ratio values of 2.5-3.0 ml interfered with the crystals, thus resulting in a higher ratio of strain and dislocations. It was confirmed that the successful bonds between the MPA functional groups were formed through the Fourier-transform infrared spectroscopy (FTIR) technique, where characteristic Cd-O, C-O, O-H, and S-H resonances became more distinct with increments of at an equivalent ratio. Optical characterizations were carried out under UV-Visible spectroscopy, and the absorption edge was nearly redshifted upon the addition of Sn and MPA. At high levels of doping and standard capping, the optical bandgap varied between 5.5 eV and 1.812 eV. Analysis using photoluminescence (PL) showed the existence of a number of emission lines relating to the oxygen vacancies and surface states. The surface passivation was the greatest, and non-radiative recombination was lowest, as the sample with 2ml of MPA covering resulted in the greatest PL intensity. Therefore, nanoparticles with the highest performance were acquired at 2 mL concentration of MPA, 1.5% Sn-doping, and 350°C calcination. The optimized parameters produced nanoparticles of very fine structural with tuneable optical properties, hence they can be considered as the most likely candidates to serve as photoanode materials in cheap and clean solar cells. This study offers new information on the synthesis of semiconductor materials in the engineering of new energy transducers.