Green and red electrophosphorescent devices consisting of cabazole/triarylamine-based polymers doped with iridium complexes

Abstract

Two types of polymers were synthesized such as poly[ N-( 2- ethylhexyl) carbazole- altN-( 4- aminophenyl) carbazole] ( PECAC) and poly[ N-( 2- ethylhexyloxy- phenyl) carbazole-alt- N-( 4- aminophenyl) carbazole] ( PEPCAC). These polymers are designed to have carbazole groups with wide band gap and a triarylamine moiety with a hole transporting property. Green and red phosphorescent polymer light emitting diodes ( PhPLEDs) were fabricated with an emitting layer consisting of either PECAC or PEPCAC as a host matrix with suitable iridium complexed, Ir( ppy)(3) as a green or IR- PIQCH as a red dopant, respectively. Red PhPLEDs doped with IR- PIQCH exhibited maximum EL emission peaks at 620nm with higher luminescence and lower driving voltage, due to effective energy transfer from host polymers to IR- PIQCH red dopant. Based on HOMO and LUMO levels of the polymers and Ir( ppy)(3), however, the synthesized polymers could not be served as suitable host polymers for Ir( ppy)(3) green dopant. Ir( ppy)(3) doped PhPLEDs exhibited red shift and wide range of EL emission