Free inert gas protection, low temperature, non-injection synthesis of CdS and doped quantum dots for efficient white light-emitting diodes

Cadmium based chalcogenides (CdS, CdSe, CdTe) quantum dots exhibited ultrahigh photoluminescence (PL), quantum yields (QYs) and multicolor luminescence. However, the usual synthesis needs high temperature, inert gas protection, and localized injection operation, which hinder applications seriously. Here, we synthesized CdS QDs and a series of metal-ions-doped QDs using low temperature synthesis (30-80 degrees C). The synthesis was designed according to supersaturated recrystallization. It was operated under air atmosphere, in DMF solution, free from inert gas protection and used non-injection operation. The obtained QDs exhibit strong and stable luminescence. They have a monodisperse, uniform morphology and good crystallinity. With increasing synthesis temperature, the emission center of the CdS QDs shifts from 500 nm to 550 nm. The metal ions doped in the CdS substrate form a deep level. The emission energy decreases and the emission center shifts to longer wavelengths. The emission peaks located at 520 nm, 534 nm, 540 nm, 578 nm and 625 nm correspond to CdS QDs doped with Sn2+, Sb3+, Ni2+, Mn2+ and Cu2+, respectively. The increased synthesis temperature also results in a red shift of the emission peak. The tunable optical properties and the suitability for large scale production endow the metal-ions-doped CdS QDs with promising potential for lighting and displays, which was demonstrated by white light-emitting diodes with a high CRI value, power efficiency and good stability.