Low-Temperature Synthesis of Highly Efficient, Deep-Red Zn-Cu-In-Se/ZnSe Fluorescence Quantum Dots

We report a facile synthesis method on CuInSe2 (CISe)-based quantum dots (QDs) by using tri-n-octylphosphine selenium (TOPSe) as selenide precursor, with assistance of oleylamine (OAm) and n-dodecanethiol (DDT). We demonstrate that the OAm and DDT jointly contribute to the formation of the low-temperature-decomposable metal-sulfide clusters, and promote the QD nucleation at relatively low temperature range of 180-200 degrees C. Furthermore, to improve fluorescence property, Zn-doping and ZnSe coating are simultaneously carried out. The obtained deep-red ZnCISe/ZnSe QDs possess higher quantum yield of 65% at wavelength of 670 nm, which is in the best performance range ever reported. Then, we investigate the improvement mechanism, where the sufficient Zn replacement of In sites is the crucial factor. This modified core-shell structure provides two benefits, on the one hand, the enhancement on intrinsic defect-related recombination, and the other hand, the improved core-shell interface that reduces the nonradiative recombination