Structure-function relationships of conjugated polyelectrolyte electron injection layers in polymer light emitting diodes

The characteristics of conjugated polymer light-emitting diodes containing poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene) as the emissive layer and cationic or anionic conjugated polyelectrolytes (CPEs) as the electron injection layer are reported. Structure variations involving backbone, type of counterion, and charge were used to establish structure-function relationships. More efficient electron injection from Al and better device performance are attained with CPEs bearing negative charges. For cationic CPEs having the same counterion but different conjugated structures, one observes better device efficiency using the material with higher electron mobility. Thus, both charge and backbone are important for optimizing device performance.