【作者】 杨涛；

【导师】 钱妍；

【作者基本信息】 南京邮电大学 ， 光学工程（专业学位）， 2021， 硕士

【摘要】 低成本、高效、稳定的白光电致发光二极管（WOLEDs,White Organic Light-Emitting Diodes）一直是有机光电子领域的热点之一。传统WOLEDs利用不同颜色发光组分间的不完全能量传递实现白光发射,但能量传递程度难以精确控制,导致器件色坐标不稳定、重复性及良品率低,此外,根据自旋量子理论,大多数荧光分子只能利用25%的单线态激子,导致机电致发光二极管（OLED,Organic Light-Emitting Diodes）器件的最大外部量子效率（EQE,External Quantu Efficiency）通常不超过5%。相比之下,磷光材料和热延迟荧光材料由于可以充分利用三线态激子可实现100%的激子利用率。然而,磷光材料稀缺、成本高,而热延迟荧光材料则由于空间电荷分离导致发光效率低下及长寿命三线态激子累积湮灭导致器件效率滚降严重,这些都限制了WOLED的进一步发展。近年来,可通过高能级快速反向系间窜越的“热激子”材料兼具了高激子利用率及效率滚降较低的优势而备受关注。本文设计并合成了两种激发态分子内质子转移（ESIPT,Excited State Intramolecular Proton Transfer）黄色荧光材料HDAPD-1和蓝绿色荧光材料HDAPD-2,这两种材料均可利用高级反向系间窜越实现了高激子利用率（70%-88%）,其分子激发态均具有显著的杂化局域-电荷转移激发态（HLCT,Hybridized Local Excited and Charge-Transfer）特性。值得一提的是,这两种化合物在溶液中均表现出高能量单线态（S₂或S₃）和最低单线态（S₁）同时发射的反Kasha规则的特性。其中基于HDAPD-1的OLED器件显示色坐标（Commission Internationale d’Eclairage,CIE）为（0.4513,0.4521）的黄光发射,最大EQE为4.12%,在黄光ESIPT荧光OLED材料中处于较高水平;基于HDAPD-2的分子在薄膜中保持了溶液态的双重发射,其蓝白光OLED的CIE坐标为（0.2317,0.3418）,最大EQE高达5.60%,目前这是报道的最高性能的单分子白光荧光OLED材料。进一步,我们制备了由不同比例的黄光发射材料HDAPD-1和DMAC-DPS的天蓝色TADF发射材料组成的非能量转移型白光薄膜,并以此为发光层,制备了非能量传递型的单发光层WOLEDs。其中,冷白光和纯白光OLED的CIE坐标分别为（0.2589,0.3567）和（0.3209,0.3225）,最大EQE分别为13.3%和9.66%,其电致发光光谱呈现出良好的色度稳定性。该工作为实现低成本、高效、结构简单、可重复制备和色坐标稳定的WOLEDs提供了新思路。更多还原

【Abstract】 Low cost,high-efficiency and highly stable white light emitting diodes（WOLEDs）are always one of the hot issues in the field of organic optoelectronics.Traditional WOLED realizes white light emission based on incomplete energy transfer between different color luminous components,but faces the problem that the energy transfer degree between different emitters is difficult to finely control,resulting in unstable color coordinates,low reproducibility and low production yield.In addition,according to spin quantum theory,only 25%singlet excitons can be utilized for most fluorescent molecules,resulting in the maximum external quantum efficiency（EQE）of the fluorescent OLED devices gnenerally not exceeding 5%.In comparation,the phosphorescent and thermally activated delayed fluorescence（TADF）materials were able to achieve 100%extion efficiency due to full use of triplet exitons.However,the phosphorescent materials are rare and expensive,whereas the TADF materials exhibit low luminous efficiency due to space charge separation and significant efficiency roll-off due to triplet-involved annihilation caused by the teiplet cumulaton during its long-lifetime.This also limits the further development of WOLEDs.In recent years,"hot-exciton"materials which can rapidly undergo fast reverse intersystem crossing through high energy levels have attracted numorous attentions because of their advantages of both high exciton utilization rate and prohibited efficiency roll-off.Herein two excited-state intramolecular proton transfer（ESIPT）yellow fluorescent material HDAPD-1 and bluish-green fluorescent material HDAPD-2 with high efficiency of exciton utilization（70%to 88%）of Hybridized Local Excited and Charge-Transfer（HLCT）states by use of fast high-level reverse intersystem crossing have been designed and synthesized.Notably,both compounds exhibit anti-kasha characteristics of simultaneous emissions in solutions from high energy level singlet state（S₂or S₃）as well as lowest singlet state（S₁）.OLED Device based on HDAPD-1 shows yellow light emission with a Commission Internationale d’Eclairage（CIE）of（0.4513,0.4521）,and maximum EQE of 4.12%,which is among the best performance in yellow ESIPT fluorescent OLEDs.HDAPD-2 remains such dual emissions in films,with its blue-white OLED exhibiting a CIE coordinate of（0.2317,0.3418）and maximum EQE up to 5.60%.This is among the highest performance for single molecular white emitting fluorescent materials.By fabricating nonenergy-transfer white emitting films consisting of different ratios of yellow emitting HDAPD-1 with sky-blue TADF emitter of DMAC-DPS,high-performance and color-stable non-energy-transferred single-EML cold white and pure-white WOLEDs have been realized,with CIE coordinates of（0.2589,0.3567）and（0.3209,0.3225）,and maximum EQEs of 13.3%and9.66%,respectively.This work pave ways for realizing simple structured low-cost,high efficiency,highly reproducible and color-stable WOLEDs.更多还原