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

Li, Dongyu, Bai, Jinke, Zhang, Tingting, Chang, Chun, Jin, Xiao, Huang, Zhen, Xu, Bing, Li, Qinghua
Chemical communications 2019 v.55 no.24 pp. 3501-3504
chemical compounds, chemical reactions, commercialization, light emitting diodes, quantum dots
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.