ZnSe/ZnS Core/Shell Quantum Dots with Narrow Emission Bands for QLED Displays

As an alternative to toxic Cd-based blue light-emitting quantum dots (QDs) and chemically unstable perovskite ones, heavy-metal-free and stable ZnSe QDs have great potential for quantum dot light-emitting diode (QLED) displays. Through overcoming the challenge of controllable synthesis of ZnSe QDs with desirable properties, this work reported the synthesis of super-narrow-band blue-emitting ZnSe/ZnS core/shell QDs with full width at half-maximum (FWHM) of photoluminescence/electroluminescence as narrow as 19/20 nm, peaked at 446/449 nm, respectively. The crystallization of the core/shell QDs was well controlled by systematic optimization on the molar ratios of cations to anions and the amount of precursor addition. The coating shell of ZnS, which has a wider band gap than ZnSe, could effectively suppresses the fluorescence tail in the emission spectrum that is caused by defects on the ZnSe core surface, narrowing the FWHM of the emission spectrum and increasing the fluorescence quantum yield of ZnSe/ZnS core/shell QDs. The prepared QLED using ZnSe/ZnS core/shell QDs exhibits superior color purity, particularly suitable for display applications. This work opens up a new route to synthesizing heavy-metal-free ultra-narrow-band blue-emitting QDs.