有机材料激子发光的温度特性

基于实验和理论模拟研究了12~320 K温度范围内八羟基喹啉铝[tris-(8-hydroxyquinoline)aluminum,Alq]和一种高效红光染料甲基2叔丁基6(1,1,7,7四甲基久咯呢定基9烯基)4H 1吡喃[4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran,DCJTB]的光致发光(photoluminescence,PL)随温度的变化,提出三种不同电荷分离程度的激子参与的Alq的稳态光致发光过程,通过拟合参量得到了三种激子的能量差值和辐射复合几率之比,观察并解释了DCJTB发光光谱从200 K以下到室温的升温过程中发生的蓝移。认为变温光致发光有可能用于评估材料的发光和导电性能,比较并讨论了有机和无机发光材料激子发光的温度特性,认为低温下小分子发光材料倾向于分子态,随温度升高逐渐向半导体态转变,Alq在150~190K之间开始发生这种转变,而DCJTB则从300~320 K开始。

Temperature-Dependent Luminescence Originating from the Recombination of Excitons in Organic Light-Emitting Materials

Based on experimental measurement and theoretical simulation,the temperature dependence of the photoluminescence(PL) of amorphous thin films of tris-(8-hydroxyquinoline) aluminum(Alq) and 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran(DCJTB) has been studied.It is proposed that three types of excitons with different charge separations are involved in the steady state PL process,which,with increasing energy,are accordingly called intra-molecule localized,intra-molecule delocalized,and inter-molecule delocalized,while the corresponding radiative decay rates are relatively low,high,and negligible,respectively.The blue shift of the DCJTB PL spectra with increasing temperature has been observed and explained.It is suggested that the temperature-dependent PL could be possibly used to evaluate the radiative and conductive characteristics of organic emitters and to distinguish whether a given material would be of molecular or semiconductor properties.