Electroluminescence in conducting polymers based on poly(phenylene ethynylene)

Electroluminescence (EL) in various conducting polymers (CP) based on poly(phenylene ethynylene) (ROPPE) which have C-C triple bond in their main chains were studied. EL in Al/CP/ITO structure utilizing copolymer based on ROPPE and pyridine as CP was blue-green and stronger than that in same structure utilizing well-known poly(dialkoxy-p-phenylene vinylene) (ROPPV). However, weaker red EL was observed in same structure utilizing copolymer based on ROPPE and anthracene. These result suggests that the increased band gap energy and improve exciton confinement efficiency, due to shortened conjugate length, were realized by introduction of C-C triple bonds in main chain of conducting polymers such as ROPPV, while these effects of C-C triple bonds are suppressed by introduction of electron-rich moiety such as anthracene which should increase effective conjugation length. Electrochemical studies on these copolymers also confirmed this interpretation.