Stable Blue Phosphorescence Iridium(III) Cyclometalated Complexes Prompted by Intramolecular Hydrogen Bond in Ancillary Ligand
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- 作者：Seungjun Yi ; Jin-Hyoung Kim ; Yang-Jin Cho ; Jiwon Lee ; Tae-Sup Choi ; Dae Won Cho ; Chyongjin Pac ; Won-Sik Han ; Ho-Jin Son ; Sang Ook Kang
- 刊名：Inorganic Chemistry
- 出版年：2016
- 出版时间：April 4, 2016
- 年：2016
- 卷：55
- 期：7
- 页码：3324-3331
- 全文大小：528K
- ISSN：1520-510X
文摘
Improvement of the stability of blue phosphorescent dopant material is one of the key factors for real application of organic light-emitting diodes (OLEDs). In this study, we found that the intramolecular hydrogen bonding in an ancillary ligand from a heteroleptic Ir(III) complex can play an important role in the stability of blue phosphorescence. To rationalize the role of intramolecular hydrogen bonding, a series of Ir(III) complexes is designed and prepared: Ir(dfppy)2(pic-OH) (1a), Ir(dfppy)2(pic-OMe) (1b), Ir(ppy)2(pic-OH) (2a), and Ir(ppy)2(pic-OMe) (2b). The emission lifetime of Ir(dfppy)2(pic-OH) (1a) (τem = 3.19 μs) in dichloromethane solution was found to be significantly longer than that of Ir(dfppy)2(pic-OMe) (1b) (τem = 0.94 μs), because of a substantial difference in the nonradiative decay rate (knr = 0.28 × 105 s–1 for (1a) vs 2.99 × 105 s–1 for (1b)). These results were attributed to the intramolecular OH···O═C hydrogen bond of the 3-hydroxy-picolinato ligand. Finally, device lifetime was significantly improved when 1a was used as the dopant compared to FIrpic, a well-known blue dopant. Device III (1a as dopant) achieved an operational lifetime of 34.3 h for an initial luminance of 400 nits compared to that of device IV (FIrpic as dopant), a value of 20.1 h, indicating that the intramolecular hydrogen bond in ancillary ligand is playing an important role in device stability.