Dependence of the Photoluminescence of Hydrophilic CuInS2 Colloidal Quantum Dots on Cu-to-In Molar Ratios
Copper indium sulfide (CIS) quantum dots (QDs) are attractive as potential optoelectronic devices, since they have large absorption coefficients across a broad spectral range, size- and composition-tunable photoluminescence from the visible to the near-infrared, and low toxicity. However, CIS QDs should be hydrophilic in certain applications. In this present work, hydrophilic CIS and CIS/ZnS colloidal QDs were synthesized by a one-pot environmentally-friendly route employing N,N-dimethylformamide (DMF) as the solvent and in situ generated H2S as the sulphur precursor. The effect of stoichiometry was investigated by varying the feeding molar ratios of Cu/In, which did not affect the crystalline structure of the CIS colloidal QDs, while the optical property was influenced significantly. With the decrease of the feeding molar ratios of Cu/In, the band gap of the resulting CIS colloidal QDs had blue-shifts and relative photoluminescence quantum yield of the corresponding CIS/ZnS colloidal QDs increased monotonically.