Optimization of annealing temperature for pulsed laser deposited CZTSSe solar cells and its improved efficiency

The Pulsed Laser Deposition (PLD) method was used to synthesize Cu2ZnSn(S, Se)4 (CZTSSe) thin layers for use in solar cell technology. The prepared thin films were subjected to annealing performed at different temperatures, such as 200 °C, 300 °C, 400 °C, and 500 °C. The effect of annealing temperature on performance of solar cell was examined. FE-SEM analysis showed that the CZTSSe thin films were highly dense, adherent, and free of voids. X-ray diffraction analysis of both as-prepared and heat-treated films showed a significant peak at the (112) plane, indicating the presence of the Kesterite phase without any additional secondary phases. The crystallite size by Debye Scherrer and W–H method was found to be nearly equal. The compressive strain was observed from the W–H plot for all the CZTSSe thin films. The UV–visible spectroscopy was employed for optical study and the energy band gap values were found in the range 0.92 eV to 0.99 eV for annealed samples. The Urbach energy values were calculated and found to be decreasing as there is an increase in annealing temperature. The Raman spectroscopy of the CZTSSe thin films revealed the creation of the Kesterite phase as well as the formation of a favorable MoS2 layer. The stoichiometry of CZTSSe thin films was revealed using energy-dispersive X-ray analysis and all the films were found to be stoichiometric. The thin films made of CZTSSe material cells showed an efficiency of 4.8%.