DESIGN AND APPLICATION OF ELECTRON-TRANSPORTING ORGANIC MATERIALS

Operating lifetime is the main problem that complicates the use of pol ymeric light-emitting diodes (LEDs). A class of electron transport (ET ) polymers [poly(aryl acrylate) and poly(aryl ether)s] is reported in which moieties with high electron affinities are covalently attached t o stable polymer backbones. Devices based on poly(p-phenylenevinylene) (PPV) prepared with these materials exhibited a 30-fold improvement i n stability and, in one case, dramatically lower (10 volts versus abou t 30 volts) operating voltage relative to those having conventional ET layers. The current-carrying capacity of indium tin oxide-PPV-polymer ic ET layer-aluminum LEDs was also increased by a factor of 30. These improvements lead to an enhancement in power efficiency of nearly an o rder of magnitude. Choosing polymers with high glass transition temper atures increases device lifetime.