Syntheses, photoluminescence and electroluminescence of four heteroleptic iridium complexes with 2-(5-phenyl-1,3,4-oxadiazol-2-yl)-phenol derivatives as ancillary ligands

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2014-01, Vol.2 (6), p.1116-1124
• Main Authors: Li, Hong-Yan, Li, Tian-Yi, Teng, Ming-Yu, Xu, Qiu-Lei, Zhang, Song, Jin, Yi-Ming, Liu, Xuan, Zheng, You-Xuan, Zuo, Jing-Lin
• Format: Article
• Language: English
• Subjects: Current efficiency
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C3TC31915F

Four new iridium(iii) cyclometalated complexes (Ir1-Ir4) with 4-trifluoromethylphenylpyridine as the main ligand and 2-(5-phenyl-1,3,4-oxadiazol-2-yl)-phenol and its fluoro/trifluoromethyl substituted derivatives as ancillary ligands have been developed. All complexes are green phosphors ( lambda sub(max) = 519-537 nm) with photoluminescence quantum efficiency yields of 10-53% in CH sub(2)Cl sub(2) solutions at room temperature, respectively. The organic light emitting diodes (OLEDs) with the structure of ITO/TAPC (1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane, 60 nm)/Ir complexes (8 wt%):SimCP2 (bis[3,5-di(9H-carbazol-9-yl)phenyl] diphenylsilane, 30 nm)/TPBi (1,3,5-tri(1-phenyl-1H-benzo[d]im idazol-2-yl)phenyl, 90 nm)/LiF (1 nm)/Al (100 nm) show good performances. In particular, device G4 based on complex Ir4 (2-(5-pentafluorophenyl-1,3,4-oxadiazol-2-yl)-phenol as ancillary ligand) showed superior performances with a peak current efficiency ( eta sub(c)) of 70.48 cd A super(-1) and a peak external quantum efficiency ( eta sub(ext), EQE) of 19.7%. This study demonstrates that the ancillary ligand attached with the 1,3,4-oxadiazole group could facilitate charge trapping across the bulk of the device for efficient OLEDs.