Microstructural and morphological properties of spin-coated Cu₂MnSn(S,Se)₄ thin films for solar cell applications

Cu₂MnSn(S,Se)₄ (CMTSSe) thin films were fabricated by using spin-coating and following selenized for different temperature. Single-phase CMTSSe films have been formed in the temperature range of 500–540 °C. Both XRD patterns and Raman measurements reveal that the selenization temperature drives the films exhibited high crystallinity and strong preferred orientation in the (1 1 2) plane. The excessive elevated selenization temperature during the grain growth would lead to the decomposition of CMTSSe phase and severe Sn loss. Further morphological studies indicate an abrupt transition from a smooth and dense microstructure to a roughness structure with many voids. The band gap energy of the CMTSSe films varied from 1.43 to 1.52 eV relying on the element loss during selenization. The solar cell device with the CMTSSe layer selenized at 540 °C achieved the highest open circuit voltage of 444 mV.