Acridone‐Based Host Materials for Green Phosphorescent and Thermally Activated Delayed Fluorescent OLEDs with Low‐Efficiency Roll‐Offs. Issue 71 (2nd November 2022)

• Record Type: Journal Article
• Authors: Yao, Ruijuan; Liu, Di; Wan, Huihui; Mei, Yongqiang; Wang, Jiahui; Cai, Rui; Zhang, Huimin; Zhao, Yuzhen; He, Zemin
• Is Part Of: Chemistry. Volume 28:Issue 71(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-11-02
• Subjects: acridone -- bipolar host materials -- low roll-off -- PhOLEDs -- thermally activated delayed fluorescent OLEDs; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202202269
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: By linking the carbazole unit to the nitrogen atom of acridone through phenyl or pyridyl, two compounds, named 10‐(4‐(9H‐carbazol‐9‐yl)phenyl)acridin‐9(10H)‐one (AC‐Ph‐Cz) and 10‐(5‐(9H‐carbazol‐9‐yl)pyridin‐2‐yl)acridin‐9(10H)‐one (AC‐Py‐Cz) were designed and synthesized. These two materials, characterized with highly twisted and rigid structure, good thermal stability, and balanced carrier‐transporting properties, were employed as host materials for green phosphorescent and thermally activated delayed fluorescent organic light‐emitting diodes (OLEDs). The carbazole group, despite its small contribution to the highest occupied molecular orbitals (HOMOs) of these two materials, plays an essential role as an intramolecular host in energy delivering and improving the hole transporting ability of these two hosts. The incorporation of the electron‐deficient pyridyl group as a linking group slightly improves the electron transporting capability of AC‐Py‐Cz. The green phosphorescent OLED (PhOLED) based on AC‐Py‐Cz exhibited excellent device performance with a turn‐on voltage of 2.5 V, a maximum power efficiency and an external quantum efficiency ( η ext ) of 89.8 lm W −1 and 25.2 %, respectively, benefitting from the better charge‐balancing ability of AC‐Py‐Cz host due to the presence of the pyridyl bridge. More importantly, all the devices based on these two hosts showed low efficiency roll‐off at high brightness due to the suppressed non‐radiative transition in the emitting layer. In particular, the AC‐Py‐Cz‐hosted green PhOLED exhibited an efficiency roll‐off of 1.6 % from the maximum next at a high brightness of 1000 cd m −2 and a roll‐off of 15.9 % at an extremely high brightness of 10000 cd m −2 . This study manifests that acridone‐based host materials have great potential in fabricating OLEDs with low efficiency roll‐off. Abstract : By combining carbazole and acridone units through pyridyl bridge, a bipolar host with highly twisted and rigid structure is developed, which guarantees the green phosphorescence and thermally activated delayed fluorescence OLEDs to exhibit remarkably low efficiency roll‐offs.