High‐Performance Nondoped Organic Light‐Emitting Diode Based on a Thermally Activated Delayed Fluorescence Emitter with 1D Intermolecular Hydrogen Bonding Interactions

Abstract Nondoped organic light‐emitting diodes (OLEDs) have drawn enormous attention for their merits of process simplicity, reduced fabrication cost, and phase stability. Herein, a novel approach of utilizing intermolecular hydrogen bonding for enhancing performance of nondoped OLEDs with a new thermally activated delayed fluorescence (TADF) emitter 10‐(4‐(2,6‐di(pyrimidin‐5‐yl)pyridin‐4‐yl)phenyl)‐10 H ‐phenoxazine (DPmP‐PXZ) is investigated. Endowing with suitable intermolecular hydrogen bonds linking the ends of neighboring DPmP‐PXZ molecules, the molecules tend to form extended 1D molecular chain in solid. This 1D structure effectively keeps the electron‐rich PXZ cores in neighboring molecules apart from each other such that triplet‐related exciton quenching can be well suppressed. In addition, it also improves the balance of carrier mobilities and the optical out‐coupling from the emitting layer. With these merits, OLEDs using DPmP‐PXZ as a dopant emitter, from 10 to 100 wt%, can maintain high external quantum efficiencies (EQEs) of over 20%. More importantly, its nondoped OLED shows a yellow emission and an excellent maximum EQE of 21.8% with little efficiency roll‐off which is even comparable with state‐of‐the‐art yellow OLEDs. These results provide new insight on the role of hydrogen bonding in molecular packing and its subsequent influences on the performance of OLEDs.