The band gap energies EG of the lithium compounds have been measured by transmittance and reflectivity measurements as well as measurements of the diffuse reflectivity. At room temperature EG=2.83 eV (LiInSe2), EG=3.56 eV (LiInS2), EG=3.13 eV (LiGaSe2) and EG=3.62 eV (LiGaS2) have been obtained presupposing a direct interband transition. In a first attempt the birefringence of LiInS2 was studied by transmittance measurements. Using infrared and Raman spectroscopy the lattice vibrational properties have been investigated.

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Thin films of lead tin sulphide PbSnS2 were deposited on glass substrates at 100 °C at vacuum pressure of 3×10–6 mbar using a thermal evaporation method. Scanning electron microscopy (SEM) and X‐ray characterization revealed that thin films were monophase and polycrystalline. The average particle size was approximately 28 nm. Absorption coefficient of PbSnS2 thin films (∼105 cm–1) was found from transmission optical spectroscopy measurements. Its fundamental absorption edge is shown to be 1.65 eV with direct allowed transition recommended for photovoltaic application. Thermoelectric measurements showed the materials to be p‐type in nature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)