Water-soluble polyfluorenes as an electron injecting layer in PLEDs for extremely high quantum efficiency

A study was conducted to demonstrate the synthesis of novel poly(9,9-bis(6'-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9, 9-bis(2-(2-mrthoxyethoxy)ethyl)-fluorene))dibromide, bound with mobile alkali or alkaline earth metal ions without their counter ions. The study also demonstrated the use of these water-soluble polymers as an electron injection layer (EIL) in the polymer light-emitting diodes (PLEDs). It was demonstrated that water-soluble poly(ethylene glycol) (PEG), blending with ionic salt between the emitting layer and the Al cathode improved device efficiency, by increasing the built-in potential. It was also observed that the device efficiency increased significantly, when the water-soluble polymer was inserted between the emitting layer and the high-work function Ag cathode in PLEDs.