Highly efficient polymer phosphorescent light-emitting devices based on a new polyfluorene derivative as host

Abstract

Several highly efficient iridium-complex polymer light-emitting devices (PLEDs) are fabricated, with a newly synthesized blue conjugated polymer, poly[(9,9-bis(4-(2-ethylhexyloxy)phenyl)-fluorene)-co-(3,7-dibenziothiene-S,S-dioxide15)] (PPF-3,7SO15), chosen as host. High luminous efficiencies of 7.4 cd·A−1 and 27.4 cd·A−1 are achieved in red and green PLEDs, respectively, by optimizing the doping concentrations of red phosphorescent dye iridium bis(1-phenylisoquinoline) (acetylacetonate) (Ir(piq)) and green phosphorescent dye iridium tris(2-(4-tolyl)pyridinato-N, C2′) (Ir(mppy)3). Furthermore, highly efficient white PLEDs (WPLEDs) with the Commission Internationale de l'Eclairage (CIE) coordinates of (0.35, 0.38) are successfully produced by carefully controlling the doping concentration of the iridium complex. The obtained WPLEDs show maximal efficiencies of 14.4 cd·A−1 and 10.1 lm·W−1, which are comparable to those of incandescent bulbs. Moreover, the electroluminescent spectrum of the white device with an initial luminance of about 1000 cd·m−2 is stable, subject to constant applied current stress, indicating that good device stability can be obtained in this system.