Synthesis of CuInS2-ZnS quantum dots for different Cu/In ratios by one-pot method and its applications to white light-emitting diodes

This paper reports one-pot method toward the synthesis of CuInS₂/ZnS hybrid nanoparticles. First, CuInS₂ quantum dots (QDs) were synthesized in the noncoordinating solvent octadecene using copper chlorine, indium chlorine and dodecanethiol. Copper indium sulfide (CIS) quantum dots (QDs) for different Cu/In molar ratios of 1/1, 1/2, and 1/4 are synthesized. The band gap energy of CIS QDs is observed to be dependent for Cu/In ratio, exhibiting a higher band gap from more Cu-deficient QDs. The emission wavelengths of all CIS QDs belong to a deep red region (710-780 nm) with relatively low quantum yields (QYs) of 3.4-7.8%. Compared to respective original core QDs, the absorption peaks of CIS/ZnS QDs are blue-shifted, and their emission wavelengths move to a higher energy accordingly, showing a quite tunable emission from yellow to red. The effective surface passivation by a ZnS overlayer results in a dramatic increase in QY of CIS/ZnS QDs in the range of 38-48%. Finally, high luminescent CIS/ZnS QDs with high luminescent PL efficiency are used for white light emitting diode.