화학공학소재연구정보센터
Thin Solid Films, Vol.670, 68-75, 2019
Effect of incorporation of sulphur on the structural, morphological and optical studies of CdSe thin films deposited by solution processed spin coating technique
Ternary compound semiconductor CdSexS1-x (x = 1, 0.8, 0.6, 0.4, 0.2 and 0) thin films were prepared on glass substrates by using simple solution processed spin coating technique. Cadmium acetate, sodium selenosulfate and thiourea were used as source materials for Cd2+, Se2- and S2- ions, while triethanolamine was used as a capping agent. The 25% concentred NH4OH solution was used as a complex reagent and also used to adjust the pH of the final solution similar to 11. The deposition conditions (rotation speed 2000 rpm for 30 s and substrate dried in the air at 120 degrees C for 2 min) were remain same for all the samples. The as-deposited thin films on glass substrate were annealed at 350 degrees C for 30 min. The X-ray diffraction pattern shows that all the samples were polycrystalline in the nature with hexagonal structure. The most of prepared thin films were highly textured along (002) plane and peak position for plane (002) is shifted with change in composition 'x'. The average crystallite size in CdSexS1-x thin films were found between 62.6 nm to 93.4 nm. Scanning electron microscopy images showed uniform deposition morphology with spherical shaped grains distributed over entire glass substrate. Samples CdSe0.8S0.2 and CdSe0.6S0.4 thin films indicated interesting morphological features with the combination of spherical shaped nanoparticles and interconnected nanofibers which form hierarchical flowerlike microstructure. Energy dispersive X-Ray studies confirmed that thin films were having approximately same stoichiometry of atomic ratio of elements Cd, Se and S as present in volumetric ratio of the reactants in chemical solution. Fourier transform infrared studies confirmed the formation of the Cd(Se,S) bonding in materials. The optical band gap of CdSexS1-x thin films were found as direct band gap in the range of 1.82 eV to 2.32 eV. As the incorporation of sulphur element increases, the band gap of CdSexS1-x thin film also increases. The CdSexS1-x thin films can be used as absorption layer in solar photovoltaic cell which is due to wide and fine tenability of the energy band gap.