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/Alq 3 (emitting green light)/Alq 3 :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 Alq 3 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.