Single-layer white polymer light-emitting diodes based on an iridium (III) complex containing alkyltrifluorene picolinic acid

To explore the relationship between the electronic properties of a host/dopant system and obtain a high-efficiency single-dopant white polymer light-emitting device two novel blue-emitting cyclometalated iridium (III) complexes of (dfppy)(2)lr(Tfl-pic) and (dfppy)(2)lr(Brfl-pic) have been synthesized and characterized, where dfppy is 2-(2,4-difluorophenyl)pyridine, Tfl-pic and Brfl-pic are picolinic acid derivatives containing trialkylfluorene and dibromoalkylfluorene units bridged with an alkoxy chain, respectively. Both iridium (III) complexes exhibited blue emission in dichloromethane solution and their neat films, and possessed good dispersibility and thermal properties. Two different devices using (dfppy)(2)lr(Tfl-pic) as a single component emitter and a blend of poly(N-vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as the host matrix were fabricated. Improved white emission was obtained by adjusting the electron injection layer leading to efficient exciplex emission. (C) 2011 Elsevier Ltd. All rights reserved.