LAUSR

Maintaining high power efficiency (PE) under high brightness is still a pressing problem for the practical application of organic light-emitting diodes (OLEDs). Here, ultrahigh-efficiency green phosphorescent OLEDs (PHOLEDs) with a record-low voltage at luminance above 5000 cd m-2 are fabricated, by developing a novel anthracene/pyridine derivative as the electron-transporting material (ETM) combined with a material displaying thermally activated delayed fluorescence as the host. The pyridine units of the ETM not only facilitate charge injection, but also enhance the electron-transporting mobility, profiting from the closely packed molecules caused by the intermolecular H-bonding. The optimized green PHOLEDs show record-low driving voltages of 2.76 and 2.92 V, with EQEs/PEs of 28.0%/102 lm W-1 and 27.9%/97 lm W-1 at 5000 and 10 000 cd m-2 , respectively. Furthermore, device optimization exhibits an unprecedented high PE of 109 lm W-1 at 10 000 cd m-2 with voltage under 3 V. Those values are the state-of-the-art among all reported green OLEDs so far, paving their way toward practical applications.