Evolution of emission manners of organic light-emitting diodes:From emission of singlet exciton to emission of doublet exciton

The emission manners of organic light-emitting diodes（OLEDs） have experienced almost three-decade evolution.In this review,we briefly summarized the emission manners of OLEDs including：（ⅰ） emission from singlet exciton;（ⅱ） emission from triplet exciton;（ⅲ） emission from singlet exciton converted from triplet exciton.Then we introduced a new type of OLEDs with the emission from doublet exciton,wherein organic neutral radicals are used as emitters.Due to the spin-allowed transition of doublet excitons,using neutral radicals as emitters is believed to be a new way to break the 25%upper limit of internal quantum efficiency of OLEDs.The progress of emissive stable neutral radicals is also shortly reviewed.

卤素原子的引入对二苯甲基自由基光稳定性、光物理性质及电致发光器件性能的影响

通过在\%N\%-咔唑基-二(2,4,6-三氯苯)甲基自由基(CzBTM)的咔唑基团的3和6位引入卤素原子,合成了3个新的自由基分子(3,6-二氟-N-咔唑基)二(2,4,6-三氯苯)甲基自由基(F 2CzBTM)、(3,6-二氯-N-咔唑基)二(2,4,6-三氯苯)甲基自由基(Cl 2CzBTM)及(3,6-二溴-N-咔唑基)二(2,4,6-三氯苯)甲基自由基(Br 2CzTM).通过对比3个自由基分子与CzBTM的理论计算结果、电化学性质、光物理性质以及光稳定性,发现对于电子给-受体型的发光自由基,其光物理性质是外围取代基团的电负性和分子空间构型共同作用的结果.Cl 2CzBTM和Br 2CzTM具有较高的光致发光荧光量子效率,而F 2CzBTM在光照下具有最长的光致发光半衰期.与以CzBTM为发光层制备的电致发光器件相比,以Cl 2CzBTM和Br 2CzTM为发光层制备的有机电致发光器件的光谱均发生了蓝移,器件的最大外量子效率均有所提高,分别是其1.8倍和2.5倍.