Highly reduced efficiency roll-off with 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-containing unit on bipolar host for improved OLEDs device lifespan

Abstract

The electrical, thermal, and optical properties of the host material used in the light-emitting layer of a thermally activated delayed fluorescence organic light-emitting diode (TADF-OLED) directly affect its efficiency, lifetime, and color. In this study, a new host material was designed, synthesized, and then applied to a green TADF-OLED device to evaluate its performance as a host. The host material was designed in a bipolar configuration, ensuring the balanced introduction and transport of electrons and holes. This balance was achieved by incorporating a carbazole unit to facilitate hole injection and transport. Moreover, a 5,9-dioxa-13b-boranaphtho [3,2,1-de]anthracene (DOBNA) unit containing a boron atom was introduced for electron injection and transport. These units were linked to ortho terphenyl spacers. The DOBNA unit improved the electron transport properties, the thermal stability of molecule, and anionic bond dissociation energy. Consequently, the device evaluated using the DOBNA-introduced material as a host for 4CzIPN, a TADF dopant, enhanced the performance by ∼ four times from LT80@1000 nit to 15.1 h compared to the unipolar host material comprising carbazole and ortho-terphenyl.