Abstract

A major factor affecting the efficient operation of polymer light-emitting diodes (LEDs) is the balancing of charge injection and transport in the devices. In an effort to address this issue we have investigated poly(2,5-pyridinediyl) (PPY) as an electron-transporting polymer (ETP). PPY is solution-processable from formic acid, and has excellent resistance to electrochemical^[1] and photo-oxidation^[2]. We synthesised PPY by oxidative coupling of 2,5-dibromopyridine with a nickel(O) catalyst^[1], and the resulting material had a high photoluminescence quantum yield of 30%. We have fabricated polymer LEDs consisting of poly(p-phenylene vinylene) (PPV) as a hole transporting and emissive layer and PPY as an electron transporting layer. For comparison we have fabricated single layer devices. Figure 1a shows light-output as a function of current density for single and bilayer diodes. Figure 1b shows the electroluminescence spectrum of a bilayer device. This spectrum is similar to that of a single layer PPV diode, with an emission peak at 560 nm.

© 1998 IEEE