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Blue quantum dot light-emitting diodes with high luminance by improving the charge transfer balance

Author:
Li, Dongyu, Bai, Jinke, Zhang, Tingting, Chang, Chun, Jin, Xiao, Huang, Zhen, Xu, Bing, Li, Qinghua
Source:
Chemical communications 2019 v.55 no.24 pp. 3501-3504
ISSN:
1364-548X
Subject:
chemical compounds, chemical reactions, commercialization, light emitting diodes, quantum dots
Abstract:
The development of blue quantum dot light-emitting diodes (QLEDs) lags far behind that of the red and green ones, which hinders the practical commercialization of QLEDs. Balancing the charge transfer still remains a challenging task, because blue QD emitters have a deeper valence band (VB) that creates a great injection barrier impeding the hole transfer. Herein, we demonstrate that the charge transfer balance can be improved by using a tert-butyldimethylsilyl chloride-modified poly(p-phenylene benzobisoxazole) (TBS-PBO) blocking layer. The TBS-PBO acts well in blocking excess electron injection and preserving the emission efficiency of the QD emitter. Compared to the insulating blocking layers, TBS-PBO has good conductivity, thus keeping the current density at a high level. Our device delivers a notable luminance of 4635 cd m⁻² at an external quantum efficiency (EQE) maximum of 17.4%. To the best of our knowledge, the luminance with EQE > 17% is the highest one to be reported for blue QLEDs.
Agid:
6332162