Bright and efficient green ZnSeTe-based quantum-dot light-emitting diodes with EQE exceeding 20

Ternary ZnSeTe quantum dots (QDs) are recognized as promising eco-friendly emitters for blue quantum-dot light-emitting diodes (QD-LEDs) and are capable of extending their emission range to green or even red light. Although extensive investigations have enabled significant advances in the external quantum efficiency of blue ZnSeTe QD-LEDs, unfortunately, the lack of effective defect passivation strategies for green and red ZnSeTe QDs poses difficulties in improving device performance, thereby impeding their development. Here, we propose to enhance the luminescence performance of green ZnSeTe devices by inserting an ultrathin ZnSeS interlayer to fabricate efficient QDs. This strategy enables us to achieve gradient thick-shell QD structures, thereby alleviating lattice mismatch at the shell-shell interface and passivating surface defects. These improvements result in enhanced quantum efficiency, improved optical stability, and elevated band position. These combined features enhance exciton recombination and promote charge injection balance, leading to a record-breaking external quantum efficiency of 20.6% and a high brightness of 106,054 cd m^-2, accompanied by an improved operational stability.