One-pot synthesis of homoleptic iridium (III) dyes created using alkoxo-functionalized bipyridine ligands and these dyes' applications for organic light-emitting diodes

• Published in: Dyes and pigments 2017-02, Vol.137, p.378-383
• Main Authors: Lee, Chiheon, Kim, Jinho, Choi, Jeong Min, Lee, Jun-Yeob, Kang, Youngjin
• Format: Article
• Language: English
• Subjects: Blue phosphorescence; Homoleptic iridium compounds; Phosphorescent organic light-emitting diodes (PHOLEDs)
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2016.10.033

A facile, one-pot synthetic method to prepare alkoxo-functionalized homoleptic cyclometalated Ir (III) compounds with facial geometry has been developed. The reaction of Ir(COD)2BF4 with two bipyridine ligands, 2′,6′-dimethoxy-4-methyl-2,3′-bipyridine and 2′,6′,4-trimethoxy-2,3′-bipyridine, afforded the homoleptic Ir (III) compounds Ir[(RO)2(Me)pypy]3 (1) and Ir[(RO)3pypy]3 (2) in good yields. The reaction conditions highly selectively produced the aforementioned Ir (III) compounds with facial geometry. The decomposition temperatures of 1 and 2 were 387 °C and 368 °C, respectively. Both compounds exhibited intense blue phosphorescence (λmax = 452–458 nm) with excellent quantum efficiencies (ΦPL = 0.45–0.52). Phosphorescent organic light-emitting diodes (PHOLEDs) that used these compounds as the dopant material and 9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazol-3-yl)diphenylphosphine oxide as the host material have been fabricated. The electroluminescent device created using compound 1 at a doping level of 5 wt% exhibited the best performance, with an external quantum efficiency of 15.7–15.5% at a brightness of 10–100 cd/m2 and color coordinates of (0.16, 0.28) at 100 cd/m2. [Display omitted] •One-pot process to synthesize homoleptic fac-Ir (III) compounds has been developed.•The emission maximum of fac-Ir (III) compounds is in the range of 450–460 nm.•An efficiency up to 15.5% has been achieved with CIE (x, y = 0.16, 0.28).•A lifetime of PHOLEDs is greater than 1.5 h(T50) at 1000 cd/m2.