The synthesis of Cu₂ZnSnS₄ nanoparticles via an open-air solution route: influences of Zn precursor content

In the present work, Cu₂ZnSnS₄ (CZTS) nanoparticles (NPs) for use in low-cost thin film solar cells were successfully synthesized using a facile open-air solution route. Copper(II) chloride dihydrate, zinc(II) acetate dihydrate, tin(II) chloride, and thiourea were used as reagents, and oleylamine was employed as solvent. The effect of varying the Zn content in the precursor solution on the structural, morphological, compositional, and optical properties of the as-synthesized CZTS NPs was investigated via X-ray diffraction, scanning electron microscopy and transmission electron microscopy, energy dispersive X-ray spectroscopy and ultraviolet–visible–infrared spectroscopy, respectively. As observed, the properties of the as-synthesized NPs improved with increasing Zn precursor contents from 0.75 to 1.5 mmol. For instance, the crystallinity of the as-synthesized NPs improved gradually and the band gap energy was tuned from 1.28 to 1.41 eV. The Zn/Sn ratio increased from 0.51 to 0.86, whereas the Cu/(Zn + Sn) ratio decreased from 0.95 to 0.7 with increasing Zn precursor contents. The results indicated that the obtained CZTS NPs, prepared with a Zn precursor content of 1.5 mmol, are a good light-absorbing layer material for application in thin film solar cells.