Optical and electrical properties of transparent conductive oxide films of undoped and doped SnO2 and In2O3 prepared using the pyrolysis spray method were studied. The optical constants extracted from transmittance and reflectance measurements between 0.25 and 3 mu m are interpreted to give values of the direct allowed band gap (4.54 eV for SnO2:F and 3.80 eV for ITO) and the indirect forbidden band gap (2.77 eV for SnO2 and 2.90 eV for ITO). Typical SnO2:F and ITO films present high transmission ( approximately=85%) and resistivities of about (9*10-3-5*10-4) Omega cm and 10-1 Omega cm respectively. Suitable figures of merit allow a useful comparison to be made of the physical properties of the different films.

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A detailed study of the optical properties of sputtered hydrogenated amorphous silicon films with varying hydrogen concentration is presented here. The energy dependence of the absorption coefficient is looked into, in detail, from a point of view of understanding the well known Tauc rule and the alternate relations being proposed in recent years. Spectroscopic and band-structural models like Wemple–Didomenico and Penn are then utilized to analyze the optical parameters near the band-gap region of the wavelength spectra. Extensive comparisons of our results are made with those of sputtered a-Si:H films of other workers, glow discharge prepared a-Si:H, chemically vapor deposited and evaporated a-Si, and also crystalline silicon. The similarities in the variation of the optical properties of a-Si:H with increasing hydrogen concentration (or decreasing measurement temperature) to that of crystalline silicon with decreasing measurement temperature lead us to interesting conclusions. Thus, it seems that decreasing disorder (topological or thermal) in a-Si:H is equivalent to decreasing thermal disorder in c-Si, at least as far as the disorder-optical property relationships are concerned.

The theory and the experiments on thermophotovoltaic (TPV) conversion are reported in this paper. The various parameters characterizing TPV systems are studied in order to provide design information for actual converters. Both the experimental results and theoretical calculations of TPV conversion efficiency are presented for comparison. They exhibit good agreement.

An analytical procedure is presented for the calculation of the maximum of transmittance in a limited spectral region and of the efficiency of a given multilayer configuration when the thickness is altered of certain films in the stack. This refining process method is employed in examples where the spectral transmittance is improved when only a few matching layers are used for refining.