Crystallization of wide-bandgap CuAlSe2 thin films deposited on antimony doped tin oxide substrates

• Formation of wide-bandgap CuAlSe2 thin films by selenization of metallic precursors.
• ATO-coated substrates promote homogeneous crystallization of CAS films.
• CAS formation on ATO for a wide range of thicknesses and se over-pressures.
• Ohmic characteristics suitable for future application in solar cells.

Formation and crystallization of homogeneous CuAlSe2 (CAS) thin films prepared by a two stage process consisting on the selenization of evaporated metallic precursor layers has been achieved onto transparent and conductive Sb:SnO2 (ATO)-coated glass substrates. Influence on the structural, optical, morphological and compositional properties of the sample thickness and selenization conditions have been analysed. Polycrystalline CuAlSe2 samples with chalcopyrite structure and a preferential orientation along the (112) plane have been obtained on ATO-coated substrates, in a wide range of thicknesses from 0.6 to 2.0 μm, with high degree of reproducibility. Average crystallite size tends to increase and the preferential orientation remains constant with the increase of the CAS thickness and the Se amount in the selenization process. The band gap energy has ranged between 2.3 and 2.5 eV. XPS measurements have shown a slightly Cu-poor surface and homogeneous distribution of Cu and Al in depth. The CAS/ATO contacts have exhibited ohmic characteristics in all cases.

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