基于三重态激子向单重态上转换机制的内量子效率可达100%的有机电致发光器件研究

Fluorescence and phosphorescence OLED devices have been used for industry based on displays and lightings, but such two sort devices have respective shortages,i.e., lower efficiency for the former and high cosst for the latter, which handily obstructs their mass application. But Adachi group of Japan Kuyshu University has developed new method increasing the efficiency by using reverse intersystem crossing （RISC）,i.e., using the sum of prompt and delay fluorescence to achieve OLED with 100% maximal internal quantum efficiency, such a devive is being called as third generation OLED, In term of the new concept and combining with our original base investigation idea on delay fluorescence based on exciplex has been demonstrated. The studying idea is due to present of smaller △E1?3 for exceplex-type OLED which is expected that either both high internal efficiency or high power efficiency could be achieved by deeply study on photophysical mechanism and luminescence physics. Especially the study that using exceplex based on donor and acceptor with weak or no-PL to demonstrate OLED iwhich includng contribution of delay fluorescence finally，the OLED would be achjieved which presents either higher efficiency or longer working lifetime. Thus this applicvation would has would have especial basic study significance and bright application foreground.

尽管荧光和磷光OLED器件已经在显示和照明产业上得到了应用,但是，它们仍分别存在各自的不足，前者效率低和后者成本过高的不足，严重障碍了它们的大批量应用。日本九州大学Adachi 研究组开拓了利用从三重态激子向单重态反向系间串越（RISC）产生的延迟荧光提高效率的新方法，原理是利用延迟荧光和原来快速荧光的总合获得了最大内量子效率可达100%的OLED器件。国际上把这种称之为第三代OLED.根据这种新概念，结合我们的原来工作基础，提出了基于激基复合物的延迟荧光研究的思路，因为理论上激基复合物的单重态和三重态的间距（△E1?3）很小，有望通过深入的光物理机制和发光物理研究，研制出既有高的内量子效率又有高的能量效率的原型OLED,是利用弱或不发光的给体和受体材料构成的激基复合物研制OLED,使其含有延迟荧光的贡献，最终研制器件既有高效率又有长的工作寿命。可见本研究具有大的基础和应用研究意义。

热活化延迟荧光被认为是继荧光OLED和磷光OLED后的第三代OLED器件。它兼具了荧光OLED的器件结构简单、启亮电压低和磷光OLED高效率的有点。基于激基复合物的OLED展示出类似于热活化延迟荧光的特点，但是大家对它的发光机理还不完全了解，同时器件性能亟待提高。在本项目支持下，我们主要对相关问题进行了深入研究，获得的主要成果如下：（1）通过瞬态PL光谱、瞬态PL光谱、瞬态EL光谱以及磁电致发光特性的研究，确认激基复合物OLED器件的发光属于热活化延迟荧光。同时研究了器件性能的决定因素，发现器件的效率主要由发光层的PL量子效率决定，器件的载流子平衡系数在一定程度上影响器件的效率；器件高电流密度下的效率滚降由发光层的PL寿命和器件的载流子平衡系数共同决定。（2）研究了给体和受体材料的三重态能级对器件性能的影响。发现如果给体或受体材料的三重态能级低于他们所产生的激基复合物的三重态能级，激基复合物的三重态能级会向给体或受体材料的三重态能级传递能量，造成参与发光的激子损失，减低器件效率。（3）构筑了基于热活化延迟荧光的蓝光、绿光、黄光、红光器件，在此基础上通过调控能量传递机制，获得了高效率白光器件。相关研究结果共发表SCI论文26篇，其中影响因子大于3.0的论文25篇。