Breaking the Efficiency Limit of Deep-Blue Fluorescent OLEDs Based on Anthracene Derivatives.

Triplet harvesting is important for the realization of high-efficiency fluorescent organic light-emitting diodes (OLEDs). Triplet-triplet annihilation (TTA) is one triplet-harvesting strategy. However, for blue-emitting anthracene derivatives, the theoretical maximum radiative singlet-exciton ratio generated from the TTA process is known to be 15% in addition to the initially generated singlets of 25%, which is insufficient for high-efficiency fluorescent devices.

Enhanced Triplet-Triplet Annihilation of Blue Fluorescent Organic Light-Emitting Diodes by Generating Excitons in Trapped Charge-Free Regions.

Three new anthracene-cored molecules, 3,3'-(5-(10-(naphthalen-1-yl)anthracen-9-yl)-1,3-phenylene)dipyridine (AP3Py-Na), 3,3'-(5-(10-(naphthalen-2-yl)anthracen-9-yl)-1,3-phenylene)dipyridine (AP3Py-2Na), and 9,10-bis(3,5-di(pyridin-3-yl)phenyl)anthracene (ADP3Py), were synthesized to be used as an efficiency-enhancement layer (EEL) in blue fluorescent organic light-emitting diodes. Insertion of a very thin EEL (3 nm) between the deep blue emitting layer (EML) and the electron transport layer enhanced the external quantum efficiency (EQE) of the blue device by 44% compared to the device without the EEL, resulting in an EQE of 7.9% and a current efficiency of 9.

An Exciplex Host for Deep-Blue Phosphorescent Organic Light-Emitting Diodes.

The use of exciplex hosts is attractive for high-performance phosphorescent organic light-emitting diodes (PhOLEDs) and thermally activated delayed fluorescence OLEDs, which have high external quantum efficiency, low driving voltage, and low efficiency roll-off. However, exciplex hosts for deep-blue OLEDs have not yet been reported because of the difficulties in identifying suitable molecules. Here, we report a deep-blue-emitting exciplex system with an exciplex energy of 3.