Efficient, Stable Blue Light‐Emitting Diodes Enabled by Heterostructural Alteration of ZnSeTe Quantum Dot and Functionalization of ZnMgO

Abstract Environment‐benign ZnSeTe quantum dots (QDs) are regarded promising blue electroluminescent (EL) emitters alternative to Cd‐based ones for the next‐generation QD‐display platform. Herein, the core/shell heterostructural variation of blue‐emitting ternary ZnSeTe QDs by manipulating ZnSeTe core size (small versus large) and ZnSe inner shell thickness (thin versus thick), while ZnS outer shell thickness remains unaltered, is explored. EL outcomes of the resulting core/shell QDs having photoluminescence quantum yields of 59−80% within the blue color regime (454−463 nm) are found to be dependent on their heterostructural dimension, exhibiting the highest performances of 31709 cd m −2 in luminance and 11.4% in external quantum efficiency (EQE) from large‐ZnSeTe/thick‐ZnSe/ZnS QDs. Furthermore, to address the chronic issues of excessive electron injection and exciton quenching at emitting layer/electron transport layer (ETL) interface, the surface of ZnMgO (ZMO) nanoparticle (NP) is modified by bicarbonate functional species. Bicarbonate passivation not only leads to the effective reduction of defective sites on the ZMO NP surface toward the suppression of exciton quenching but induces the upshift of ETL band alignment in favor of charge balance. As a result, the optimized blue device incorporated with bicarbonate‐functionalized ZMO NPs delivers a peak luminance of 39739 cd m −2 and a maximum EQE of 17.1%.