Single Molecular Precursor Solution for CuIn(S,Se)2 Thin Films Photovoltaic Cells: Structure and Device Characteristics

A single molecular precursor solution is described for the deposition of CuIn(S,Se)2 (CIS) film onto Mo-coated glass substrates by spin coating, followed by annealing in Se atmosphere. Characterization of the films by X-ray diffraction, Raman spectroscopy and scanning electron microscopy demonstrates the formation of a highly homogeneous and compact 1.1 μm thick CIS layer, with a MoSe2 under-layer. Atomic force microscopy reveals the presence of spherical grains between 400 and 450 nm, featuring surface corrugation in the range of 30 nm. Film composition is found to be in close agreement with that of the precursor solution. Diffuse reflectance spectroscopy shows a direct band gap (Eg) of 1.36 eV. Intensity and temperature dependence photoluminescence spectra show characteristic features associated with a donor–acceptor pair recombination mechanism, featuring activation energy of 34 meV. Over 85 solar cell devices with the configuration Mo/CIS/CdS/i-ZnO/Al:ZnO/Ni–Al and an total area of 0.5 cm2 were fabric...