ZnSTe/ZnSe/ZnS Reverse Type-I Blue-emitting Quantum Dot Diodes

ZnSTe/ZnSe/ZnS core/shell/shell quantum dots (QDs) were synthesized using a single ZnS precursor to achieve blue-emitting QDs with an emission peak at 450 nm. In this structure, a small quantity of tellurium (Te) was surface-doped onto the inner-core ZnS surface positioned at the interface with the ZnSe shell. This doping suppressed the surface trap emission and induced a red-shift in the emission of the final ZnSTe/ZnSe/ZnS core/shell/shell QDs, resulting in an improved quantum yield (QY) after the application of the outer ZnS shell. These QDs exhibited a photoluminescence (PL) peak at 447 nm, a full width at half maximum (fwhm) of 35 nm, and a PL QY of 74%. The emission spectrum demonstrated excellent symmetry, with half-maxima widths of 17.3 and 18.2 nm on either side of the peak center. When incorporated into electroluminescent (EL) devices, quantum-dot light-emitting diodes displayed band–edge emission with symmetric EL spectra centered at a peak wavelength of 451 nm and a fwhm of 30 nm. These devices achieved a maximum luminance of 2200 cd/m2, an external quantum efficiency of 4.58%, and a current efficiency of 2.31 cd/A.