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The determination of optical coefficients of absorbing coatings in the far infrared spectrum on silicon substrates is considered in this paper. To find them, a technique is used based on taking into account correction associated with absorption spectra. Correction of the spectra is carried out by exploitation models of the absorbing film. Optical coefficients of BaYF5 films in the spectrum region of 1.3-27 microns were obtained. On their basis, a band-pass metal-dielectric filter was synthesized for a wavelength 5 micron.

A survey of materials options and technologies for GaSb-related thermophotovoltaic (TPV) cells is presented, followed by an overview of device design principles and issues. This device technology has been developed for thermal-to-electric generator systems with thermal emitter infrared sources operated in the 1000–1200 °C range. Significant results for the growth, material characterization and device performance of TPV cells based on InGaAsSb, InGaSb, AlGaAsSb and InAsSbP fabricated by LPE, MOCVD, MBE and diffusion methods are reviewed. For single-junction TPV cells, epitaxial heterostructures with a ~0.53 eV bandgap InGaAsSb base layer and wide-bandgap AlGaAsSb or GaSb window/cladding layers (all closely lattice matched to a GaSb substrate) represent the state of the art. As an alternative, a low-cost Zn-diffusion technology for fabrication of InGaAsSb p–n homojunction structures has been developed for producing the high efficiency TPV cells. External quantum yields as high as 90% at wavelengths (around 2000 nm wavelength), and response edges to about 2400 nm wavelength have been obtained with these TPV cells. Multijunction tandem TPV devices based on GaSb top cells and InGaAsSb bottom cells provide even higher performance. TPV cells based on InAsSbP, also reviewed here, have spectral responses in wavelengths in the 2.5–3.5 μm range, and thus provide a means for utilizing radiation from thermal emitters with lower temperatures.

Forward dark and load I - V characteristics of triple-junction GaInP/Ga(In)As/Ge solar cells (SCs) in the temperature range 300 - 80 K have been studied. At temperatures below 200 K, jumps of current and voltage in, respectively, dark and load characteristics were observed experimentally and attributed to the existence of a counter potential barrier formed by isotype heterolayers between the tunnel diode and the Ge p-n junction in the InGaP/Ga(In)As/Ge SC. An analysis of the forward dark characteristics of GaInP/Ga(In)As/Ge SCs, recorded at 80 K, enabled evaluation of the potential and real conversion efficiencies of incident sunlight. The influence exerted by the shape of the side mesa surface of GaInP/Ga(In)As/Ge SCs on the dominant current flow mechanisms was analysed. A method for single-step separate etching was suggested and studied. This method allows one to reduce surface leakage currents and raise the yield of suitable SCs with an efficiency greater than 35% at low sunlight concentrations (C = 10 - 100, T = 300 K). The suggested post-growth technology reduces the number of fabrication operations and the SC production cost and improves the reliability of the SC operation in a wide temperature range.