Oleic acid-mediated ZnSeTe core and its interface engineering for narrow-emission blue-quantum dot light-emitting diodes

ZnSeTe quantum dots (QDs) represent a promising class of cadmium-free emitters for pure-blue quantum dot light-emitting diodes (QLEDs) in next-generation high-definition displays. However, efficient blue emission typically requires high tellurium (Te) doping, which induces oxidation, generates surface defects, and broadens the emission spectrum, thereby limiting device efficiency and scalability. To overcome this challenge, we precisely tune the molar ratio of zinc to oleic acid (OA) in the precursor to achieve controlled enlargement of the ZnSeTe cores while simultaneously lowering the Te content, effectively narrowing the full width at half maximum (FWHM) with red shift of the emission peak. Furthermore, to counteract Te's sensitivity to oxygen and moisture, an in-situ ZnSe shell is grown via a one-pot synthesis. This shell suppresses Te oxidation during purification, reduces non-radiative recombination losses, and enhances both chemical stability and photoluminescence. After further coating with ZnSe and ZnS shells, the resulting QDs exhibit a pure blue emission peak at 459 nm with a FWHM narrowed to 23 nm and a photoluminescence quantum yield (PLQY) of 50%. Blue QLEDs based on these QDs achieve an improved maximum external quantum efficiency (EQE) of 12.69. This work demonstrates that the synergistic integration of OA-mediated size regulation and core/shell interface engineering offers a viable pathway toward high-performance, cadmium- and lead-free blue QDs for efficient QLEDs.