Mechanism of enhanced quantum efficiency in light-emitting diode based on a poly(p-phenylenevinylene) derivative

Transient electroluminescence (EL) measurements were made for a indium-tin- oxide (ITO)/poly[(2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) -p-phenylenevinylene] (PPPDPV)/Al organic light-emitting diode (OLED), wher e PPPDPV is a derivative of poly(pphenylenevinylene) (PPV) carrying the ele ctron-transporting 2-(4-biphenyl)-5-(4-t-butylphenyl-1, 3,4-oxadiazole) moi eties directly attached to the PPV backbone. As a result, we were able to e xplain the superior external quantum efficiency of a PPPDPV OLED device by a faster mobility as well as a longer EL lifetime in comparison to those fo r a PPV device. (C) 2000 American Institute of Physics. [S0021-8979(00)0810 5-6].