Structural and optical properties of CZTS nanoparticles prepared by a colloidal process

This research presents the influence of copper (Cu) concentration on the properties of copper zinc tin sulfide (CZTS) nanoparticles (NPs) synthesized by a colloidal method, employing oleylamine as an organic solvent. From the structural analysis, a pure phase of CZTS was obtained at an optimized molar ratio of 1.8:1.1:1:4, and secondary phases were observed as the Cu concentration increased. The increment of the NPs size from 15 to 50 nm was noticed as a function of Cu concentration. Importantly, the optical bandgap energy was tuned from 1.35 to 1.68 eV with respect to Cu concentration. The sample synthesized at the molar ratio of 1.8:1.1:1:4 showed a pure phase CZTS with desired elemental composition and bandgap. Furthermore, CZTS thin films were prepared by a doctor-blade method using synthesized NPs followed by annealing under a sulfur/nitrogen atmosphere. The annealed CZTS film showed a significant improvement in the morphological, electrical and optoelectronic properties. Thus, the annealed CZTS film can be efficiently used as an absorber layer in low-cost thin film solar cells.