There is lot of research work at enhancing the performance of energy conversion and energy storage devices such as solar cells, supercapacitors, and batteries. In this regard, the low bandgap and a high absorption coefficient of CdSe thin films in the visible region, as well as, the low electrical resistivity make them ideal for the next generation of chalcogenide-based photovoltaic and electrochemical energy storage devices. Here, we present the properties of CdSe thin films synthesized at temperatures (below 100°C using readily available precursors) that are reproducible, efficient and economical. The samples were characterized using XRD, FTIR, RBS, UV-vis spectroscopy. Annealed samples showed crystalline cubic structure along (111) preferential direction with the grain size of the nanostructures increasing from 2.23 to 4.13 nm with increasing annealing temperatures. The optical properties of the samples indicate a small shift in the bandgap energy, from 2.20 to 2.12 eV with a decreasing deposition temperature. The band gap is suitably located in the visible solar energy region, which make these CdSe thin films ideal for solar energy harvesting. It also has potential to be used in electrochemical energy storage applications.
This paper describes the deposition and characterization of CeO2/ZnO and CeO2/NiO coreshell thin films with emphasis on the effect of post deposition temperature on the optical properties and structural patterns. The structural temperature-dependent analysis indicated different XRD patterns for both films. However, both films are polycrystalline as depicted by the various peaks in the XRD diffractograms. The SEM images for both films differ in terms of their particle aggregation and distribution. The dependence of the transmittance, absorption coefficient, band gap, refractive index, extinction coefficient, imaginary dielectric constant on annealing temperature were investigated. The results showed that the transmittances of the films were significantly reduced by the heat treatments. The transmittance reduced from 92% to 65% for CeO2/ZnO film samples and 63% to 30% for CeO2/NiO film samples. The band gap showed considerable variation with annealing temperatures. The band gaps of all samples were in ranges of 1.75–3.85 eV and 3.50- 3.88eV for CeO2/ZnO and CeO2/NiO core-shell thin films respectively. The values of the energy band gap strongly indicate that the films can be used in different optoelectronic applications including solar photovoltaic.
Quaternary thin films of Cu2S/Fe2O3 have been synthesized via simple, inexpensive and highly reproducible chemical bath deposition technique. The grown films were characterized with Rutherford backscattering technique (RBS), X-ray diffractometer (XRD), scanning electron microscope (SEM), and spectrophotometer for compositional, structural, morphological, and optical properties respectively. The multiple peaks exhibited by the various XRD patterns of the films showed that the films are polycrystalline while the SEM analysis showed an increase in grain size and uniformity of grain distribution as temperature increases. The absorbance (A), transmittance (T), absorption coefficient ( ), band gap ( g ), extinction coefficient (k), real ( r ) and imaginary dielectric ( i ) constants were modified by thermal annealing. The optical and solid state analysis for Cu2S/Fe2O3 thin films indicate that A ≤ 0.66, T ≤ 92 %, ≤ 1.70 x 106m -1 , g increases from 3.75-3.85 eV, k ≤ 3.75, r ≤ 8.5 and i ≤ 2.05. The high transmittance in the infrared region of Cu2S-Fe2O3 thin films deposited suggest that the films can be used as coating materials for the construction of poultry houses in order to protect young chicks which have not developed protective thick feather from UV radiation while admitting the heating portion of electromagnetic spectrum into the house for warming young chicks. Based on the wide band gap exhibited by all the quaternary thin films, they are promising materials for window layers in solar cell fabrication and fabrication of optoelectronic devices, etc.
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