Post-Annealing Influence on Structural, Surface and Optical Properties of Cu3BiS3 Thin Films for Photovoltaic Solar Cells

In this work, thin films of Cu₃BiS₃ were deposited with the usages of non-vacuum chemical route for use in inexpensive photovoltaic solar cells. The post-annealing influence on the structural, morphological, wettability along with optical properties was explored with the support of X-ray diffraction (XRD), scanning electron microscopy (SEM), water contact angle (WCA) and optical spectra correspondingly. The XRD reveals that the Cu₃BiS₃ thin films annealed at 773 K were polycrystalline with an orthorhombic structure. Raman spectrum exhibited three distinct vibrational peaks at about 169, 290 and 470 cm⁻¹, confirming the establishment of wittichenite Cu₃BiS₃ with orthorhombic structure. SEM shows the formation of well-defined nano-spherical grains of average size of 150 nm with a huge surface area. The hydrophobic nature of Cu₃BiS₃ thin film was transformed into hydrophilic with rise in post-annealing temperature. The Cu₃BiS₃ thin films exhibited a high absorption coefficient of ~10⁵cm⁻¹ and direct bandgap between 1.72 and 1.47 eV, indicating that Cu₃BiS₃ has a potential candidate in solar cell as an absorber layer. Our collective endeavours are in progress to fabricate photovoltaic (PV) solar cells based on Cu₃BiS₃ with a suitable buffer layer and a study of its I-V characteristic.