Preparation of Cu(In,Al)(Se,S)2 Thin Films by Low-Cost Non-vacuum Hybrid Process

Cu(In,Al)(Se,S)₂ thin films were successfully obtained through a simple low-cost non-vacuum process. The Cu(In,Al)Se₂ raw material powder was firstly synthesized by a tra-ditional solvothermal route. Then, the precursor coatings were prepared by drop-coating Cu(In, Al)Se₂ slurry. Finally, the Cu(In,Al)Se₂ and Cu(In,Al)(Se,S)₂ films were achieved by the selenization and/or sulfuration process. Through X-ray diffraction (XRD), scanning electron microscope, X-ray fluorescence, and absorption spectroscopy measurement, it was found that all the films show the single chalcopyrite phase structure and have the preferred(112) orientation. Meanwhile, after substituting selenium by sulfur, the main XRD peaks shift to higher 2θ degrees and the porous films become more compact. The energy band gap also increases to a suitable range for light absorption from 1.21 eV to 1.33 eV, which indicates that the additional sulfuration process is much more favorable for improving the quality of Cu(In,Al)(Se,S)₂ films.