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The optical properties of CuIn 1−x Ga x Se 2 epitaxial single-crystal layers were determined by spectroscopic ellipsometry (SE) and complementary photoreflectance spectroscopy (PR) in dependence of composition. Accurate values of refractive index n and extinction coefficient κ and values of the fundamental and higher band-gap energies of quaternary selenides were obtained for six different Ga concentrations: x = 0.08, 0.19, 0.22, 0.50, 0.55, 0.82. In addition, for CuIn 1−x Ga x Se 2 with x = 0.08 and 0.55, variable-angle ellipsometric measurements were performed. Only a very small contribution of the extraordinary component to the measured effective dielectric function was found, which implies that, in chalcopyrite single-crystal layers, the extraordinary component cannot be separated by altering the angle of incidence.

The structural and optical properties of technologically interesting pyrolytic carbons formed from cured novolac resin and cured novolac/biomass composites were studied by X-Ray Diffraction Analysis (XRD), and Fourier Transform Infrared (FTIR), Raman and Photoluminescence (PL) spectroscopy. Pyrolysis of the cured materials took place at temperatures in the range 400-1000 degrees C. The most important weight loss, shrinkage and structural changes of pyrolyzed composites are observed at temperatures up to 600 degrees C due to the olive stone component. In the same temperature range, the changes in pyrolyzed novolac are smaller. The spectroscopic analysis shows that novolac pyrolyzed up to 900 ( degrees )C has less defects and disorder than the composites. However, above 900 ( degrees )C, pyrolyzed novolac becomes more disordered compared to the pyrolyzed composites. It is concluded that partial replacement of novolac by olive stone in the composite materials leads to the formation of a low cost, good quality product.

The optical properties of CuIn 1−x Ga x S 2 (CIGS) polycrystalline films and solar cells were characterized by room and low (20 K) temperature photoreflectance (PR) and electroreflectance (ER) spectroscopy for two different compositions of the CIGS absorber ([Ga]/([In]+[Ga]) = 0.04 and 0.12). The E a and E b band energies of the three-split energy gap of ternary and quaternary absorbers were determined at room (300 K) and low (20 K) temperatures. In the ER spectra at 300 K, the E a and E b bands were split into four sub-bands originated by differently strained regions of the active absorber layer. The strain evolution in the layer was analysed with respect to the band separation. Modulated reflectance was proven to be a versatile tool for the investigation of material properties. The results of the present study are discussed together with the results of SEM and XRD studies.

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