Surfactant-mediated solvothermal synthesis of CuSbS2 nanoparticles as p-type absorber material

The novel chalcostibite CuSbS2 had gained unique attention due to their dynamic nature as less toxic, cost-effective and earth abundant materials for the synthesis of an absorber layer in solar cell application. Herein, a facile and effective solvothermal method was used to enhance the sphere-like grain growth in the presence of polyvinylpyrrolidone (PVP) along with other precursor's, followed by the deposition of CuSbS2 thin films using drop casting method. The synthesized nanoparticles and the deposited films were characterized for their structural, morphological, optical and electrical properties using different characterization techniques. X-ray diffraction (XRD) and Raman analysis revealed that as the amount of PVP increased, the crystallinity improved and the impurity phase formation reduced. High-resolution transmission electron microscope (HRTEM) with reduced crystallite size in the range of 2-5 nm and field emission scanning electron microscope (FESEM), exhibited sphere-shaped grains indicating the effect of PVP as surfactant for the growth of CuSbS2 nanomaterials. The average elemental composition of the nanoparticles had been determined using EDX analysis, and the result yielded Cu rich in all the samples. Optical studies using UV-Vis-NIR diffuse reflectance spectroscopy revealed that obtained CuSbS2 nanoparticles were having the absorption in the entire visible region and the direct band gap energy was in the range of 1.25 eV to 1.53 eV and that of photoluminescence spectrum gave the emission in the near IR region. The hall measurement studies showed that the deposited CuSbS2 films exhibited p-type conductivity. Devices were fabricated with the configuration of FTO/n-TiO2/p-CuSbS2/Ag, and the electrical properties were studied by recording the current- voltage (I-V) characteristics of the heterojunction device structures.