用于蓝色有机电致发光二极管的宽带隙有机半导体的退化机制研究

Organic Light-Emitting Diodes (OLEDs) based display and lighting technologies are receiving broad attention in recent years, however, blue OLEDs still have some drawbacks in key technical specifications (especially stability). Wide bandgap organic semiconductors (WBGOSs) are key elements of blue OLEDs, thus in-depth investigation of the degradation mechanism of WBGOSs is of great importance for the realization of stable blue OLEDs. The degradation processes of WBGOS are a series of complex chemical reactions that involve the dissociation and recombination of chemical bonds and the degradation products are usually acting as defects. Recent research indicates that degradation products of common WBGOSs could emit light at long wavelength region, which provides a more intuitive means of the detection method for the study of the degradation mechanism of WBGOS. Based on the luminescent properties of degradation products of WBGOSs, we will carry out the following research topics: 1) the relationship of the ligand structure of WBGOS and luminescent properties of its degradation products; 2) The effect of environment molecules on the degradation processes of WBGOS. The proposed research will provide new experimental evidence for the understanding of the degradation mechanism of WBGOS and support the design and synthesis of stable WBGOS.

近年来基于有机电致发光二极管（OLED）的显示与照明技术近来得到广泛关注，但蓝色OLED在关键技术指标上（尤其稳定性）仍有较大差距。宽带隙有机半导体材料（以下简称WBGOS）是蓝色OLED的必要组成部分，深入揭示WBGOS的退化机制是实现稳定蓝色OLED的关键所在。WBGOS的退化过程是一系列复杂的化学反应过程（化学键的断裂与重新组合），退化产物通常作为缺陷存在。研究发现，常见WBGOS的退化产物可在长波段发光，该现象为WBGOS的退化机制研究提供了一种更为直观的检测手段。本课题拟基于WBGOS的发光退化产物开展以下研究：1）WBGOS的结构单元与其退化产物发光的对应关系，（2）周围环境分子对WBGOS的退化过程的影响。本课题将为揭示WBGOS的退化机理提供新的实验基础，从而为实现稳定WBGOS的分子设计与合成提供参考。

宽带隙有机半导体是有机电致发光二极管（OLED）技术的关键材料基础，对于实现高效稳定的OLED尤其是蓝光OLED具有重要意义。本项目重点关注宽带隙有机半导体的退化过程研究，选取具有代表性的两种宽带隙有机半导体CBP和TAPC开展深入研究，重点开展以下两方面的研究内容：1）利用客体掺杂TAPC调控其热激子过程，研究其对退化速率的影响；2）CBP的热激子过程在高性能OLED中的机理及应用。项目取得以下发现：1）分别利用荧光染料Alq3、磷光染料Ir(ppy)2acac以及过渡金属氧化物MoO3掺杂TAPC，观察掺杂客体对TAPC的退化特征峰随时间的影响规律，其中荧光染料分子可以将退化速率显著降低，将退化速率常数降低了25倍，磷光染料次之，大约可以降低3倍，而过渡金属氧化物不能抑制初期的分子退化，但是可以抑制后期的退化；2）基于CBP的三线态-三线态淬灭（TTA）可以将Alq3的电致发光效率从4 cd/A提升到超过8 cd/A，在该器件中探测到了激子扩散对发光过程的贡献。