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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