激子复合区随温度移动对OLED磁效应的影响

制备了DCM掺杂层靠近阴极的双发光层有机发光器件ITO/CuPc/NPB/Alq3（发射绿光）/Alq3：DCM（发射红光）/LiF/Al,并在不同温度下测量了该器件和无DCM掺杂的单发光层参考器件的磁电致发光（Magneto-ElectroLuminescence,MEL）和磁电导（Magneto-Conductance,MC）.在注入相同电流密度下,发现双发光层器件MEL的高场（B50mT）效应随温度降低呈现先减小后增大的非单调变化,这与单发光层参考器件的单调递增变化明显不同.同时测量了不同温度下的电致发光光谱,发现双发光层器件的533nm和600nm两个特征峰的强度随温度变化出现了此消彼长的现象,表明激子复合区域随温度变化发生了移动.通过分析工作温度对器件各发光层中的三重态激子对间相互作用及载流子迁移率的影响,对双发光层器件中MEL的高场效应随温度的非单调变化进行了定性解释.实验结果进一步验证了在单发光层器件中得到的有机磁效应高场变化的相关结论.

Influence of exction recombination zone movement with the changing temperature on the magnetic field effect in OLED

Organic electroluminescence devices, with the structure of ITO/CuPc/NPB/Alq3（emitting green light）/Alq3：DCM（emitting red light）/LiF/Al（double emitting layers device） and single light-emitting layer reference device, have been fabricated in this paper. The magnetic field effects on electroluminescence and current （MEL and MC） are studied under different temperatures. The results show that the high field effect （B〉0 mT） of MEL in double emitting layers device decreases first, then turns to increase with decreasing temperature. In contrast, the single light-emitting layer device increases monotonically, at the same injection currents. Moreover, the two spectral peaks at 533 nm and 600 nm in double emitting layers device coming from DCM and Alq3 respectively, show one falling and the other rising with decreasing temperature, which indicates the exction recombination region shifting with changing temperature. The nonmonotonic changes in the high field effect of the MEL are discussed, and in terms of the triplet-triplet interaction and carrier mobility change with the working temperature.