Substrate-Dependent Characteristics of CuSbS2 Solar Absorber Layers Grown by Spray Pyrolysis

Abstract

Copper antimony sulfide (CuSbS2) is an affordable and eco-friendly solar absorber with an optimal bandgap and high absorption coefficient, and it stands out as a promising candidate for thin-film solar cells. This study investigates the effects of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and glass substrates on the microstructural, morphological, and optical properties of CuSbS2 (CAS) layers synthesized via spray pyrolysis. X-ray Diffraction (XRD) and Raman spectroscopy analyses revealed that CAS phases formed on ITO and FTO substrates exhibited a phase composition without additional copper phases. However, the CAS layer on glass contained a copper sulfide (CuS) phase, which can be detrimental for solar cell applications. Furthermore, the influences of the substrate morphology and contact angle on the growth mechanisms of CAS layers was examined, highlighting the relationship between the substrate micromorphology and the resultant film characteristics. Advanced image processing techniques applied to Atomic Force Microscopy (AFM) images of the substrate surfaces facilitated a comprehensive comparison with the surface characteristics of the CAS films grown on those substrates. Field Emission Scanning Electron Microscopy (FESEM) indicated that CAS layers on ITO possessed larger grains than FTO, whereas those on FTO exhibited lower roughness with a more uniform grain distribution. Notably, the optical properties of the CAS layers correlated strongly with their microstructural and morphological characteristics. This work highlights the critical influence of substrate choice on the growth and characteristics of CAS layers through a comparative analysis.