Suppressing the secondary phases via N2 preheating of Cu2ZnSnS4 thin films with the addition of oleylamine and/or 1-Dodecanethiol solvents

The demand for a reliable alternative renewable energy is skyrocketing given the detrimental effect of conventional energy sources on the environment and its rapidly depleting global supply. While Cu2ZnSnS4 (CZTS)- based photovoltaic devices have gained a foothold through enhanced energy conversion efficiency, efforts are still required to further boost the physical and chemical properties of the material for higher conversion efficiency. In this study, the impact of solvent addition on the purity of nitrogen (N2) preheating of CZTS ink formulations via the hot injection method was investigated. The CZTS inks were deposited using the spin coating technique and preheated at 150 ◦C under ambient N2 and then heated within the sulfurization process at 580 ◦C. Three types of CZTS samples were prepared comprising sulfur only, sulfur and Oleylamine (OLA), and 1-Dodecanethiol (1-DDT) dissolved in sulfur and OLA. Following the preparation of the CZTS thin films, the microstructural, vibrational, optical, and electrical properties of the thin films were performed via various analyses, including X-ray Diffraction (XRD) and Raman spectroscopy, Hall measurement, spectrophotometry, and Scanning Electron Microscope (SEM). Based on the results, the XRD patterns confirmed the formation of CZTS compounds with varying crystallite sizes, whereas the Raman analysis demonstrated that the synthesized films were composed of pure stannite phase CZTS. In addition, the sample ink with sulfur only exhibited a high crystallite size of 49 nm compared to 40 nm in the presence of OLA. Furthermore, a suitable bandgap for solar cells absorption was obtained in all samples. According to the electrical characteristics, all the p-type semiconductor samples recorded a low resistivity in the presence of 1-DDT and OLA. Overall, the sulfur/OLA/1-DDT sample demonstrated superior characteristics compared to the other materials based on its ideal surface morphology, high crystallite size, and low charge carrier concentration. The results presented in this paper demonstrated a promising approach for the synthesis of effective absorber thin films for photovoltaic applications.