Growth and characterization of sodium pentaborate [Na(H4B5O10)] single crystals.
The bulk single crystals of sodium pentaborate [Na(H4B5O10)] were grown by slow evaporation solution growth technique using deionized water as solvent. The grown crystal was confirmed by single crystal X-ray diffraction studies. The structural perfection of the grown crystals has been analyzed by high resolution X-ray diffraction (HRXRD) studies by recording rocking curve. The photoluminescence (PL), UV-vis spectral studies were performed and the optical bandgap of the material was calculated. The presence of the functional groups was identified by FT-IR measurement. The factor group analysis was done on Na(H4B5O10) to reveal the vibrational optical modes. The thermal and mechanical properties of the grown crystal were studied by TG-DTA and Vickers microhardness tester, respectively. The dielectric behavior of Na(H4B5O10) was investigated with different frequencies and temperatures.
Synthesis, growth and third order nonlinear optical studies of a rhombohedral crystal: Sodium tetraborate pentahydrate
Abstract An apt and a futuristic nonlinear optical material sodium tetraborate pentahydrate (STBPH) was synthesized and grown by the technique of slow evaporation. The structural parameters of the crystal was confirmed by single crystal XRD revealed rhombohedral crystal system. Crystal's broad optical transparency was revealed by UV–Vis absorption spectrum. From the absorption spectrum, theoretical calculations were made to determine absorption coefficient, band gap, Urbach energy and reflectance. The functional groups were identified by FT-IR and FT-Raman spectra. Vicker's microhardness measurement disclosed that the grown crystal belongs to soft material category. Photoluminescence (PL) spectral study of STBPH indicated violet and blue emission peaks respectively at 343.06 nm and at 453.11 nm, 490.19 nm. Dielectric studies reveal the dielectric nature of the grown crystal. TGA-DTA studies showed that the crystal holds good thermal stability. The third order nonlinearities of STBPH was investigated by Z-scan technique manifest its suitability in nonlinear optical applications.
Recent developments of silicon thin film solar cells on glass substrates
Abstract Among various semiconductor technologies applied in photovoltaics, thin-film technologies offer several attractive features, both technically and economically. Recent developments of silicon thin-film devices predominantly based on amorphous silicon (a-Si), are described. Particular emphasis is placed on the importance of the substrates that consist of glass coated with a transparent conductive oxide (TCO) to serve as front contact layer of the photovoltaic film combination. The electrical conductivity and optical absorption of the TCO substantially affect the energy conversion efficiency of solar modules. An essential enhancement of the light absorption within the photoactive a-Si layer is derived from a surface texture of the TCO, that provides index-grading for lower front reflection, and light scattering to result in light trapping due to total internal reflections within the a-Si. The requirements for optimal TCO properties are reviewed in the context of their availability. Additionally, novel cell structures involving microcrystalline silicon, are expected to lead to higher efficiencies. Thin-film technologies, led by those based on a-Si, will take on an increased role in module production worldwide, which is consistent with favorable manufacturing cost expectations.