The development of wide-bandgap materials deposited on transparent conducting oxides for high efficiency and low cost semitransparent photovoltaic devices or tandem cells is becoming important in the last few years. CuIn1−xAlxSe2 (CIAS) thin films with bandgap above 1.95eV for 0.7≤x≤0.9 were deposited onto bare and two different (tin-doped indium oxide, ITO and aluminium-doped zinc oxide, AZO) coated glass substrates by a two stage process consisting of the selenization of metallic precursor layers. Polycrystalline CIAS thin films orientated preferentially along the (112) plane with chalcopyrite structure were obtained. The bandgap energy increased no linearly with the Al addition. X-ray diffractograms showed the coexistence of several CIAS phases. Optical, structural and composition analysis revealed that the ITO and AZO substrates promote not only the incorporation of Se, but also a more homogenous distribution in depth regarding the CIAS samples on bare glass, and acted like a barrier to the oxidation from the glass substrate.