Jia Haoran, Wang Zhibin, Yuan Ting, Yuan Fanglong, Li Xiaohong, Li Yunchao, Tan Zhan'ao, Fan Louzhen, Yang Shihe
College of Chemistry Beijing Normal University Beijing 100875 China.
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China.
Adv Sci (Weinh). 2019 Apr 30;6(13):1900397. doi: 10.1002/advs.201900397. eCollection 2019 Jul 3.
The development of efficient red bandgap emission carbon quantum dots (CQDs) for realizing high-performance electroluminescent warm white light-emitting diodes (warm-WLEDs) represents a grand challenge. Here, the synthesis of three red-emissive electron-donating group passivated CQDs (R-EGP-CQDs): R-EGP-CQDs-NMe, -NEt, and -NPr is reported. The R-EGP-CQDs, well soluble in common organic solvents, display bright red bandgap emission at 637, 642, and 645 nm, respectively, reaching the highest photoluminescence quantum yield (QY) up to 86.0% in ethanol. Theoretical investigations reveal that the red bandgap emission originates from the rigid π-conjugated skeleton structure, and the -NMe, -NEt, and -NPr passivation plays a key role in inducing charge transfer excited state in the π-conjugated structure to afford the high QY. Solution-processed electroluminescent warm-WLEDs based on the R-EGP-CQDs-NMe, -NEt, and -NPr display voltage-stable warm white spectra with a maximum luminance of 5248-5909 cd m and a current efficiency of 3.65-3.85 cd A. The warm-WLEDs also show good long-term operational stability (/ > 80% after 50 h operation, : 1000 cd m). The electron-donating group passivation strategy opens a new avenue to realizing efficient red bandgap emission CQDs and developing high-performance electroluminescent warm-WLEDs.
开发用于实现高性能电致发光暖白色发光二极管（暖白光发光二极管）的高效红色带隙发射碳量子点（CQD）是一项巨大挑战。在此，报道了三种红色发射电子给体基团钝化的CQD（R-EGP-CQD）的合成：R-EGP-CQD-NMe、-NEt和-NPr。这些R-EGP-CQD可很好地溶解于常见有机溶剂中，分别在637、642和645 nm处显示出明亮的红色带隙发射，在乙醇中的光致发光量子产率（QY）最高可达86.0%。理论研究表明，红色带隙发射源于刚性π共轭骨架结构，而-NMe、-NEt和-NPr钝化在诱导π共轭结构中的电荷转移激发态以实现高QY方面起着关键作用。基于R-EGP-CQD-NMe、-NEt和-NPr的溶液处理电致发光暖白光发光二极管显示出电压稳定的暖白色光谱，最大亮度为5248 - 5909 cd/m²，电流效率为3.65 - 3.85 cd/A。这些暖白光发光二极管还表现出良好的长期运行稳定性（在50小时运行后/＞80%，：1000 cd/m²）。电子给体基团钝化策略为实现高效红色带隙发射CQD以及开发高性能电致发光暖白光发光二极管开辟了一条新途径。
