Effect of Deposition and Annealing Temperatures on Physical Properties of CdSe Nanoparticles Thin Film for Solar Cell Applications.

Abstract

High quality nanoparticles Cadmium Selenide, CdSe, thin films were prepared by Chemical Bath Deposition (CBD) technique. The films were deposited on glass substrate at different bath temperatures, using cadmium chloride as 〖Cd〗^(+2) ion source and sodium selenosulphite as 〖 Se〗^(-2) ion source. The pH of the bath was kept constant around 11 ± 0.1. The air annealed film at different temperatures for 1h was included in this work. The effect of chemical bath temperatures and annealing in air on structure and optical properties were studied. The structural properties were studied by X-ray diffraction for all thin films and revealed a Polycrystalline nature with cubic structure having preferential orientation along (111) plane direction. The calculated crystallite size was found to be between 4.902 nm and 7.937 nm, and this indicates that all the prepared CdSe thin films are nanoparticles. It has been found that crystallite size increases with increasing deposition temperature and annealing temperature. Optical properties were studied by UV-vis spectrophotometer for all films, which shows blue shift in the peak. The values of the energy gap (allowed direct transitions) calculated from the absorption spectra, were between 2.2 and 3 eV, in contrast to the bulk, energy gap which is 1.74 eV. The temperature dependence of electrical resistivity of CdSe nanoparticles (at powder form) measured in the temperature range of 300- 455 K. The electrical measurement results show that the electrical resistivity of the samples decreases with temperature down to 4.5×〖10〗^5 Ω cm at 455 K.