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Stable Blue Phosphorescent OLEDs Based on a Tetradentate Pt(II) Complex with Extended π-Conjugation
Pan Tong1, Feng Zhan1, Wenhao Fang1
1Center for Phosphorescent Material Research, State Key Laboratory of Green Chemical Synthesis and Conversion, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou310014, P. R. China.
None:
Achieving simultaneously high efficiency and long operational lifetime in blue organic light-emitting diodes (OLEDs) remains a major challenge. Herein, we report a newly designed blue tetradentate Pt(II) complex, PtTP, featuring a biphenyl substituent on the benzocarbene moiety to extend π-conjugation and steric tert-butyl groups to suppress aggregation, together with weak intramolecular noncovalent interactions. As a result, PtTP exhibits a high photoluminescence (PL) quantum yield of 97% in a 5 wt % poly(methyl methacrylate) (PMMA)-doped film and excellent thermal stability (Td = 500 °C). The device based on PtTP exhibits efficient blue phosphorescence with an external quantum efficiency (EQE) of 23.3% at 100 cd/m2 and maintains an EQE of 17.5% even at an ultrahigh luminance of 10,000 cd/m2, indicating remarkably small efficiency roll-off. Moreover, the device achieved significantly improved operational stability, with an LT50 of 378 h at an initial luminance of 1000 cd/m2. These results demonstrate that synergistic π-conjugation extension and steric engineering provide an effective strategy for realizing highly efficient and stable blue OLEDs.
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