Tuning magneto-electroluminescence in organic light emitting diodes by controlling the competition between singlet fission and triplet fusion

We report a tunable magneto-electroluminescence (MEL) in doped organic light-emitting diodes (OLEDs) with narrow energy gap molecule of 4-dicyanomethylene-2-t-butyl-6-1,1,7,7-tetramethy-ljulolidyl-9-4H-pyran (DCJTB) doped rubrene as active layers. It is noted that the MEL at 500 mT alters significantly from 19.3% to −1.0% by controlling the doping concentration of DCJTB in the active layer at room temperature. The results might be caused by the conversion from singlet fission to triplet fusion depending on the competition between energy transfer and charge trapping channels in doped layer. Moreover, the MEL can also be tuned by changing the working temperatures for the devices with certain doping concentration. Therefore, this work provides a feasible pathway to tune the MEL by controlling the competition between singlet fission and triplet fusion in OLEDs.