Synthesis and Photoresponse of Quinary Zinc-Blende Cu₃FeInSnS₆ Nanoplates

Quinary Cu3FeInSnS6 (CFITS) nanoplates were synthesized through a synergistic dual-cation substitution strategy using a hot-injection method, where oleylamine and 1-dodecanethiol served as coordinating ligands to guide two-dimensional growth. The nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and absorption spectroscopy. Structural analysis confirms that the CFITS nanoplates crystallize in a phase-pure cubic zinc-blende structure (space group F-43 m) without detectable secondary phases. Optical measurements reveal that the nanoplates exhibit broad and intense visible-light absorption with a direct bandgap of 1.51 ± 0.03 eV, suitable for photovoltaic applications. Under standard AM 1.5 G illumination, the CFITS film shows a clear photoresponse with a light-to-dark current ratio (Ilight/Idark) of 2.46, surpassing several related copper-based chalcogenides. This enhancement is attributed to the synergistic substitution of Fe2+ and In3+, which is proposed to effectively suppress antisite defects and improve charge transport. Furthermore, the two-dimensional geometry endows the nanoplates with a unique electronic structure that mitigates carrier recombination and facilitates interfacial charge extraction. The solution-processable CFITS nanoplate films demonstrate good atmospheric stability, maintaining performance over 24 h. This work not only expands the family of multinary copper chalcogenides but also provides a feasible strategy for designing efficient, low-cost, and earth-abundant absorber materials for next-generation thin-film solar cells.