Conjugated polymer composites for use in electrophosphorescent light-emitting diodes

Xiong Gong, The University of Akron

Abstract

High performance electrophosphorescent light emitting diodes (LEDs) were demonstrated by using conjugated polymers, poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO), PFO end-capped with hole-transporting moieties (HTM), PFO-HTM, and PFO end-capped with electron-transporting moieties (ETM), PFO-ETM, as the hosts and the organometallic emitter, tris-[2,5-bis-2'-(9,9'-dihexylfluorene) iridium] [Ir(HFP)3] as the guest. Electrophosphorescent LEDs fabricated from PFO, PFO-HTM, and PFO-ETM as the hosts emit red light with turn-on voltage around 5V, luminances (L) of 2040 cd/m2, 1937 cd/m2 and 2487 cd/m2 at 290 mA/cm2 (16 V), and luminance efficiencies (LE) of 1.40 cd/A, 1.38 cd/A and 1.80 cd/A at 4.5 mA/cm2 for PFO, PFO-HTM, and PFO-ETM, respectively. The results demonstrate that high performance electrophosphorescence can be obtained from conjugated polymer-based LEDs that are fabricated by processing the active materials directly from solution.