Surfactant free solvothermal synthesis of Cu 3 BiS 3 nanoparticles and the study of band alignments with n-type window layers for applications in solar cells: Experimental and theoretical approach

Highlights: • Cu₃BiS₃ nanoparticles were synthesized by surfactant free solvothermal method. • Phase-pure orthorhombic Cu₃BiS₃ with stoichiometric composition was obtained. • A theoretical elucidation of the electronic structure properties of Cu₃BiS₃ was performed. • Possible window materials are identified based on band edge calculations. -- Abstract: In this paper we describe the synthesis of nanoscale grains of the p-type semiconductor Cu₃BiS₃ (CBS) and its material properties. Seed-like nanograins of length ~250 nm with orthorhombic wittichenite structure were obtained through the simple solvothermal reaction of CuCl, Bi(NO₃)₃ and sulfur in ethylene diamine. The obtained nanomaterial is of single phase without traces of any impurities as confirmed by XRD, XPS, Raman spectroscopy, and TEM Fourier transform analysis. The material has a band gap 1.4 eV. The Seebeck coefficient is ~450 μV/K, which is in the range of that reported for CBS synthesized by hot pressing the components Cu, Bi and S. With the aid of Density Functional theory, the electronic structure properties of the material are evaluated to derive some photovoltaic parameters of interest. The band alignments of the CBS system with known n-type window materials such as CdS, ZnO, ZnS, CdS/ZnO, CdS/ZnS and TiO₂, were also studied to evaluate the prospect of heterojunction solar cells based on CBS absorber. This may represent a theoretical methodology to design heterojunctions with adequate window materials that enhance the performance of solar cells.