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Synthesis and optoelectronic properties of novel fluorene-bridged dinuclear cyclometalated iridium (III) complex with A-D-A framework in the single-emissive-layer WOLEDs

Organic Electronics
DOI: 10.1016/j.orgel.2014.08.014
  • Electrophosphorescence
  • Dinuclear Iridium (Iii) Complex
  • Woleds


Abstract To explore the influence of push-pull chromophores on properties of emitter in organic light-emitting devices (OLEDs), an acceptor-donor-acceptor (A-D-A)-based dinuclear iridium (III) complex of (dfppy)4Ir2(dipic-FL) was synthesized via Suzuki coupling reaction, in which dfppy is 2-(2,4-difluorophenyl)pyridine and dipic-FL is an ancillary ligand of 2,7- di(5-pyridyl-2-carboxyl)-9,9-dioctyl-9H-fluorene. An intense emission peak about 480 nm resulting from the (dfppy)2 Ir(pic) chromophore and a weak long-wavelength emission band at 580-660 nm attributed to intramolecular charge transfer transition were exhibited for (dfppy)4 -Ir2(dipic-FL) in dichloromethane solution. But a remarkably hypsochromic photolumine- scence profile with an intense characteristical emission peak at 422 nm was observed, which is attributed to the intraligand (IL) π-π∗ excited states in its thin film. White emission with a maximum luminance of 1040 cd/m2 and current efficiency of 1.2 cd/A was obtained in its single-emissive-layer (SEL) OLEDs with a configuration of ITO/PEDOT:PSS/(dfppy)4Ir2 -(dipic-FL):TCTA (10 wt%)/TPBi/LiF/Al. To our knowledge, this is one of the best examples in term of dinuclear iridium complex as single dopant in the high-performance white-emitting SEL-OLEDs.

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