We have synthesized Er2S3/ZnS core/shell QDs by employing ErSt3, ZnSt2, and sulfur as precursors via a hot solution phase chemistry using a nucleation-doping strategy. X-ray diffraction (XRD), transmission electron microscope (TEM) and photoluminescence (PL) spectra were used to characterize the structure, morphology and luminescence properties of Er2S3/ZnS core/shell QDs. Moreover, the influence of overcoating temperatures on the infrared luminescence properties of QDs was investigated. PL spectra show that the emission intensity from the 4I13/2 --> 4I15/2 transition of Er3+ strongly increases with increasing overcoating temperatures, which was interpreted by the enhancing diffusion of Er3+ ions. IR-LEDs were fabricated combining commercial red GaAs LEDs with Er2S3/ZnS QDs, and luminescence properties of the IR-LED have been investigated.