CZTS polycrystals formation by laser annealing and demonstration of solar cell fabrication

Cu2ZnSnS4 (CZTS) is a promising material for solar cells because all its constituents are earth-abundant elements, and its light absorption coefficient is ~100 times higher than that of Si. CZTS is generally formed by precursor formation followed by heat treatment at 400–600 °C. In this work, a novel CZTS formation process, which consists of Cu-Zn-Sn-S containing CZTS precursor formation followed by 445 nm laser irradiation in atmosphere, was investigated. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV-vis spectroscopy analysis revealed that the poly crystallization of CZTS precursor was promoted by increasing the output power or scan time per unit length at the laser irradiation. This suggests that the defect or secondary phase was reduced, and the precursor was changed to CZTS polycrystals by laser annealing. Finally, a CZTS thin-film solar cell was fabricated through laser annealing, with an efficiency of 0.003% under AM1.5G (100 mW/cm2) at 25 °C.