Effect of NaF evaporation on morphological and structural properties of Cu2ZnSnSe4 (CZTSe) thin film deposited by sputtering from a single compound target

Cu2ZnSnSe4 (CZTSe) is a promising semiconducting material for photovoltaic applications. In the chalcogenide materials, addition of Na helps in grain growth and improves the electrical properties by passivating the surface as well as grain boundary defects. But, the effect is not well researched for kesterite materials. In this study, CZTSe thin films were deposited by sputtering an in-house made single compound target followed by annealing it in N2 atmosphere for very short duration. Use of compound target makes the process easier and simple. Compound target has been made by mixing the binary selenides and cold pressing it. Na-doping was carried out by evaporating NaF over film made by sputtering the compound target before annealing the film. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy have been used for characterizing the samples. It has been observed that grain size increased drastically by Na doping in CZTSe thin film. Due to improved crystallinity enhancement in the intensity of XRD peaks as well as Raman peaks have been observed. Also, a slight shift in the Raman peaks towards lower wavenumber has been observed. The results have been explained. Using in-house made sputtering target and enhancing the grain growth by adding Na is the novelty of this work.