Blue light-emitting diodes based on colloidal quantum dots with reduced surface-bulk coupling
Xingtong Chen, Xiongfeng Lin, Likuan Zhou, Xiaojuan Sun, Rui Li, Mengyu Chen, Yixing Yang, Wenjun Hou, Longjia Wu, Weiran Cao, Xin Zhang, Xiaolin Yan, Song Chen
Abstract
Abstract To industrialize printed full-color displays based on quantum-dot light-emitting diodes, one must explore the degradation mechanism and improve the operational stability of blue electroluminescence. Here, we report that although state-of-the-art blue quantum dots, with monotonically-graded core/shell/shell structures, feature near-unity photoluminescence quantum efficiency and efficient charge injection, the significant surface-bulk coupling at the quantum-dot level, revealed by the abnormal dipolar excited state, magnifies the impact of surface localized charges and limits operational lifetimes. Inspired by this, we propose blue quantum dots with a large core and an intermediate shell featuring nonmonotonically-graded energy levels. This strategy significantly reduces surface-bulk coupling and tunes emission wavelength without compromising charge injection. Using these quantum dots, we fabricate bottom-emitting devices with emission colors varying from near-Rec.2020-standard blue to sky blue. At an initial luminance of 1000 cd m −2 , these devices exhibit T 95 operational lifetimes ranging from 75 to 227 h, significantly surpassing the existing records.