Solvothermal Synthesis of Phase Pure Nano-crystalline CZTSSe in Aniline for Thin Film Photovoltaic Cells

CZTSSe is composed of earth abundant, relatively inexpensive and non-toxic metal with an intermediate chalcogenide structure. Direct bandgap metal chalcogenide thin film has the potential to reduce production costs for both raw materials and processing requirements. CZTSSe has received greater attention in the field of solar cells due to its tunable bandgap for different S to Se ratio varying for pure selenide (E_g = 1.1) and pure sulfide (E_g = 1.45). The current study describes the synthesis of CZTSSe nanocrystals using a simple and cost-effective solvothermal method. This method not only reduces cost but also prevents the usage of toxic solvents and avoids the selenization route. Aniline has been used as both solvent and stabilizing agent for the formation of nanocrystals. The obtained nanocrystals were studied for their structural, morphological and optical properties using XRD, HRTEM, UV-Vis spectroscopy and XPS. The XRD and HRTEM patterns of the synthesized nanocrystals confirms the kesterite structure of CZTSSe. The UV-Vis spectra of the nanocrystal confirms the direct bandgap of about 1.187 eV. This band gap energy is very near to the ideal value for an absorber in a photovoltaic solar cell.