期刊
ADVANCED FUNCTIONAL MATERIALS
卷 30, 期 30, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202002173
关键词
emission; N-donor; near-infrared; platinum; pyrazole; pyrimidine; stacking interaction
类别
资金
- Ministry of Science and Technology (MOST)
- City University of Hong Kong
- Hong Kong SAR
- Research Grants Council (RGC) of Hong Kong
Near-infrared organic light-emitting diodes (NIR OLEDs) enable many unique applications ranging from night-vision displays and photodynamic therapies. However, the development of efficient NIR OLEDs with a low efficiency roll-off is still challenging. Here, a series of new heteroleptic Pt(II) complexes (1-4) flanked by both pyridyl pyrimidinate and functional azolate chelates are synthesized. The reduced pi pi* energy gap of the pyridyl pyrimidinate chelate, and strong intermolecular interaction and high crystallinity in vacuum-deposited thin films engender strong intermolecular charge transfer transition including metal-metal-to-ligand charge transfer; thereby, exhibiting efficient photoluminescence within 776-832 nm and short radiative lifetimes of 0.52-0.79 mu s. Consequently, nondoped NIR-emitting OLEDs based on these Pt(II) complexes are fabricated, to which Pt(II) complexes2and4give record high maximum external quantum efficiency of 10.61% at 794 nm and 9.58% at 803 nm, respectively. Moreover, low efficiency roll-off is also observed, among which the device efficiencies of2and4are at least four times higher than that of the best NIR-emitting OLEDs recorded at current density of 100 mA cm(-2).
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