Heterostructural tailoring of blue ZnSeTe quantum dots toward high-color purity and high-efficiency electroluminescence

• Extensive synthesis of deep-blue ZnSeTe QDs with double shells was implemented. • Thicknesses of ZnSe inner and ZnS outer shell were individually modulated. • Te/Se composition of blue-emissive ZnSeTe core were finely tuned. • Exceptional EQE of 18.6% was achievable from an optimal QD heterostructure. Ternary ZnSeTe quantum dots (QDs) are regarded as the most promising non-Cd blue emitters, which can be exploited for the fabrication of self-emissive QD display device or QD-light-emitting diode (QLED). We report extensive synthesis of high-quality blue ZnSeTe QDs with a double shell scheme of ZnSe inner and ZnS outer shell in a unique two-step approach. In such ZnSeTe/ZnSe/ZnS heterostructure, the thickness modulation of ZnSe inner shell leads to the variations in not only the thickness of ZnS outer shell but Photoluminescence (PL) characteristics such as peak wavelength, color purity-associated bandwidth, and Quantum yield (QY). The Te/Se ratio in ZnSeTe core is precisely tailored to demonstrate moderate PL tunability in deep-blue territory and the thickness of ZnS outer shell is further independently varied to examine its effects on the performance of QLED. All the QDs that possess outstanding PL QYs up to near-unity (96%) along with an appropriate deep-blue emissivity are individually employed for solution-processed QLED fabrication. The resulting blue QLEDs produce high electroluminescence performances in the ranges of 6107–12654 cd/m 2 in luminance and 5.3–18.6% in external quantum efficiency, depending on ZnSe inner, ZnS outer shell dimensions and ZnSeTe core composition.