High‐Efficient Deep‐Blue Light‐Emitting Diodes by Using High Quality Zn x Cd 1‐ x S/ZnS Core/Shell Quantum Dots

High‐quality violet‐blue emitting Zn x Cd 1‐ x S/ZnS core/shell quantum dots (QDs) are synthesized by a new method, called “nucleation at low temperature/shell growth at high temperature”. The resulting nearly monodisperse Zn x Cd 1‐ x S/ZnS core/shell QDs have high PL quantum yield (near to 100%), high color purity (FWHM) <25 nm), good color tunability in the violet‐blue optical window from 400 to 470 nm, and good chemical/photochemical stability. More importantly, the new well‐established protocols are easy to apply to large‐scale synthesis; around 37 g Zn x Cd 1‐ x S/ZnS core/shell QDs can be easily synthesized in one batch reaction. Highly efficient deep‐blue quantum dot‐based light‐emitting diodes (QD‐LEDs) are demonstrated by employing the Zn x Cd 1‐ x S/ZnS core/shell QDs as emitters. The bright and efficient QD‐LEDs show a maximum luminance up to 4100 cd m −2 , and peak external quantum efficiency (EQE) of 3.8%, corresponding to 1.13 cd A −1 in luminous efficiency. Such high value of the peak EQE can be comparable with OLED technology. These results signify a remarkable progress, not only in the synthesis of high‐quality QDs but also in QD‐LEDs that offer a practicle platform for the realization of QD‐based violet‐blue display and lighting.