Highly efficient, solution-processed orange-red phosphorescent OLEDs by using new iridium phosphor with thieno[3,2-c] pyridine derivative as cyclometalating ligand

A new orange iridium phosphor of (EtPy)(2)Ir(acac) with thieno[3,2-c]pyridine derivative as cyclometalating ligand was designed and synthesized. The combination of thieno[3,2-c] pyridine with rigid fluorene moiety enlarged the p conjugation of ligand, and consequently caused the peak emission of (EtPy)(2)Ir(acac) red-shift to 588 nm. By using (EtPy)(2)Ir(acac) as the orange phosphor, the fully solution-processed PhOLEDs were fabricated with the following device configuration: ITO/PEDOT:PSS/PVK: PBD:(EtPy)(2)Ir(acac)/CsF/Al. With PEDOT: PSS 8000 as the hole-injecting material, the orange device achieved a maximum current efficiency of 13.4 cd A(-1), a maximum power efficiency of 5.9 mu m W-1 and a maximum external quantum efficiency (EQE) of 11.2% with a CIE coordinate of (0.62, 0.38) that falls into the orange-red region. Moreover, at high luminance of 1000 cd m(-2), the device still remained high current efficiency of 8.7 cd A(-1) and EQE of 7.3%. To the best of our knowledge, these efficiencies were among the highest ever reported for solution-processed orange-red PhOLEDs. (C) 2013 Elsevier B. V. All rights reserved.