Effect of preheating and annealing temperature on the microstructure and optoelectronic properties of CZTS films prepared by sol-gel method

The effects of different preheating and annealing temperatures on the surface morphology, microstructure, and optical properties of Cu 2 ZnSnS 4 (CZTS) thin films are investigated by controlling the preheating and annealing temperatures. The prepared thin films were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and ultra-violet-visible (UV-Vis) spectroscopy techniques. XRD and Raman spectroscopy showed that a Kesterite structure with a selective orientation along the (112) peak was generated, and the thin films produced at a preheating temperature of 300 °C and annealing temperature of 570 °C had fewer secondary phases, which was beneficial for improving the performance of the solar cells. SEM confirms that the crystallite size increases and then decreases as the temperature increases, and the largest and most uniform crystallite size with the smoothest surface is generated at the above preheating and annealing temperatures. UV-Vis measurements show that the thin films generated at the above temperature have the lowest transmittance and the lowest optical band gap value of 1.46 eV, which is close to the optimal band gap value for solar cells and is suitable as an absorber layer material.