Article pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Molecular Engineering of Phenylbenzimidazole-Based Orange Ir(III) Phosphors toward High-Performance White OLEDs Li-Li Wen,† Chun-Xiu Zang,‡ Ying Gao,† Guo-Gang Shan,*,† Hai-Zhu Sun,† Tong Wang,§ Wen-Fa Xie,*,‡ and Zhong-Min Su*,† †
Institute of Functional Material Chemistry and National & Local United Engineering Lab for Power Battery, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People’s Republic of China ‡ State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun, Jilin 130012, People’s Republic of China § Army Armor Academy NCO Institute, Changchun 130017, People’s Republic of China S Supporting Information *
ABSTRACT: To develop B-O complementary-color white organic light-emitting diodes (WOLEDs) exhibiting high efficiency and low roll-off as well as color stability simultaneously, we have designed two orange iridium(III) complexes by simply controlling the position of the methoxyl group on the cyclometalated ligand. The obtained emitters mOMe-Ir-BQ and pOMe-Ir-BQ show good photophysical and electrochemical stabilities with a broadened full width at half-maximum close to 100 nm. The corresponding devices realize highly efficient electrophosphorescence with a maximum current efficiency (CE) and power efficiency (PE) of 24.4 cd A−1 and 15.3 lm W−1 at a high doping concentration of 15 wt %. Furthermore, the complementarycolor all-phosphor WOLEDs based on these phosphors exhibit good performance with a maximum CE of 31.8 cd A−1, PE of 25.0 lm W−1, and external quantum efficiency of 15.5%. Particularly, the efficiency of this device is still as high as 29.3 cd A−1 and 14.2% at the practical brightness level of 1000 cd m−2, giving a small roll-off. Meanwhile, extremely high color stability is achieved by these devices with insignificant chromaticity variation.
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INTRODUCTION Since the pioneering study by Kido and his co-workers,1 many researchers have paid considerable attention to white organic light-emitting diodes (WOLEDs).2 WOLEDs have been widely recognized as crucial candidates for display and lighting because of their striking features, including high electroluminescence (EL) efficiency, long lifetime, and low production cost, which are superior to the performance of incandescent lamps and fluorescent tubes.3 Substantial improvements in their performance have been realized by employing all-phosphorescent materials in the emissive layers, due to their inherent ability of utilizing all electron−hole pairs including singlet and triplet excitons for radiative decay.4 In consideration of their practical use in solid-state light, WOLEDs require not only a simple configuration but also a high EL performance. Although whiteemitting devices comprising three emission units (blue, green, and red) or more can be effective in accomplishing high-quality illumination, their complicated structures inevitably result in high driving voltage and processing complexity.5 Alternatively, more simply structured WOLEDs composed of two complementary emitters with satisfactory performance have been highlighted to make fabrication cost-effective for widespread commercialization.6 However, there is much room for improvement in device efficiency, since the theoretical value of power efficiency for WOLEDs is about 240 lm W−1.7 © XXXX American Chemical Society
Dichromatic WOLEDs exhibiting a truly high color-rendering index (CRI) remain a fascinating challenge. Aside from that, the low CRI (
