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[en] We investigated infrared-active phonons of CaTiO3, SrTiO3, BaTiO3, and Ba0.5Sr0.5TiO3 thin films, and a (BaTiO3)5/(SrTiO3)5 artificial superlattice by a Fourier transform infrared spectrometer with a grazing angle (48o) incident reflectance method. The longitudinal phonon energies of the thin films were different from those of the bulk material due to the lattice strain of the substrate. The Ba0.5Sr0.5TiO3 thin film and (BaTiO3)5/(SrTiO3)5 superlattice showed different phonon modes due to structural discrepancies, even though their chemical compositions are similar. The Ba0.5Sr0.5TiO3 thin film showed a single phonon energy lying between the phonon energies of BaTiO3 and SrTiO3 thin films, while the (BaTiO3)5/(SrTiO3)5 superlattice well preserved the characteristic phonon modes of BaTiO3 and SrTiO3 thin films.
[en] An innovative approach has been demonstrated for the deposition of Cu2ZnSnSe4 (CZTSe) absorber layers. Using a unique, safe solvent combination, moving away from hydrazine, elemental Cu, Zn, Sn and S/Se can be fully dissolved at ambient conditions, with the composition easily controlled. The preparation and the spray deposition of these solutions are performed in air, allowing a quick, easy and inexpensive process. Upon selenisation, large crystals are observed which are identified as the CZTSe kesterite phase using X-ray diffraction and Raman, the latter showing no distinctive signs of any binary or ternary secondary phases. Using this method, CZTSe absorber layers have been prepared for use in thin-film solar cells reaching efficiency of 3.2%. With further device optimisation, improved device performance will be achieved. - Highlights: • A safe and easy approach for preparing solutions of Cu2ZnSnSe4 (CZTSe) • A simple and quick deposition of CZTSe absorber layer via spray coating • Identification of CZTSe kesterite phase via Raman spectroscopy and X-ray diffraction • Efficiencies of 3.24% reached, with further device optimisation required • Overall, a low-cost and safer alternative for production of thin-film solar cells
[en] This work focuses on the fabrication of stoichiometric CuInSe2 nanostructures with controllable physical parameters of the nanocrystals suitable for hybrid organic/inorganic photovoltaics. CuInSe2 nanostructures were prepared by the chemical close-spaced vapor transport (CCSVT) method onto Mo/barrier/glass substrates by using an In2Se3 source material and Cu precursors. The In2Se3 source material was volatilized in H2 ambience with the addition of HCl vapors at 550 °C. Three different types of Cu precursors were used: (i) Cu thin films (6–250 nm thick) deposited by e-beam, (ii) Cu nanoparticles prepared by spray pyrolysis and (iii) Cu nanostructures formed by applying the nanosphere lithography (using a monolayer of 450 nm nanospheres). The CCSVT process parameters were varied to reveal the optimum conditions for the preparation of secondary phases free CuInSe2 nanostructures. The structural characterization by x-ray diffraction in both grazing incidence and Θ-2Θ configurations revealed the formation of CuInSe2 chalcopyrite phase independently on the applied precursor type. The elemental composition of the as-prepared CuInSe2 nanostructures was analyzed by laser ablation-inductively coupled plasma mass-spectrometry. In non-optimised processes, an excess of Se compared to stoichiometric composition was detected and attributed to the formation of molybdenum selenide and indium selenide phases. The formation of the latter secondary phases was suppressed by tuning the CCSVT deposition parameters. - Highlights: • CuInSe2 nanostructures were prepared by the chemical close-spaced vapor transport. • Precursors used: Cu thin films, Cu nanoparticles and nanostructures. • Cu nanoparticles prepared by spray pyrolysis. • Cu nanostructures formed by applying the shadow nanosphere lithography.