High-efficiency polymer light-emitting diodes with stable saturated red emission based on blends of dioctylfluorene-benzothiadiazole-dithienylbenzothiadiazole terpolymers and poly[2-methoxy,5-(2-ethylhexoxy)-1,4-phenylene vinylene]

High-efficiency light-emitting diodes with stable saturated red emission are realized based on blends of poly[2-methoxy,5-(2-ethylhexoxy)-1,4-phenylene vinylene] (MEHPPV) and terpolymers of dioctylfluorene, benzothiadiazole, and dithienylbenzothiadiazole (DBT). External quantum efficiency of more than 3.2 emitted photons per hundred electrons injected (ph/el %) is realized for a device with the Commission Internationale de I’Eclairage coordinates x=0.65, y=0.35. Such high device performance results from effective hole injection induced by the addition of MEHPPV, efficient energy transfer from the [0-0] ground-state emission of MEHPPV to the DBT segments together with the direct contribution of the [0-1] phonon coupling emission of MEHPPV.