High efficiency and simplified white organic light-emitting diode based on a single-host emission layer

• We report on single-host white organic light-emitting diodes (WOLEDs) based on a bipolar material, 2,6-bis[(3-carbazol-9-yl)phenyl)]pyridine (26DCzPPy), as the host.
• By engineering the device structure directed by a cascade energy transfer concept, both the device efficient and stability are considerably improved as compared to the reference device.
• We utilize Firpic as an assistant dopant to boost energy transfer from 26DCzPPy to PO-01.

Efficient white organic light-emitting diodes (WOLEDs) with high stability are highly desired nowadays to produce devices that meet the commercial illumination requirement. WOLEDs based on single-host emission layer, is a preferred route to simplify device structures and thus lower the production cost. In this work, we report on single-host WOLEDs based on bipolar material, 2,6-bis[(3-carbazol-9-yl)phenyl)]pyridine (26DCzPPy), as the host, and Iridium (III)bis[(4,6-difluorophenyl)-pyridinato-N,C2′] (FIrpic), [3,2-c]pyridinato-N,C2′) acetylacetonate (PO-01), as blue and yellow dopants, respectively. The devices exhibit not only higher efficiency, but also superior stability compared to the conventional devices and doping-free devices. Detailed analysis is conducted to clarify the underlying reasons. This work enriches the mechanism understanding of single-host devices and paves the way for development of high performance WOLEDs.

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