A novel orange-red thermally activated delayed fluorescence emitter with high molecular rigidity and planarity realizing 32.5% external quantum efficiency in organic light-emitting diodes. Issue 9 (15th July 2022)

• Record Type: Journal Article
• Authors: Zhang, Heng-Yuan; Yang, Hao-Yu; Zhang, Ming; Lin, Hui; Tao, Si-Lu; Zheng, Cai-Jun; Zhang, Xiao-Hong
• Is Part Of: Materials horizons. Volume 9:Issue 9(2022)
• Page Start: 2425
• Page End: 2432
• Publication Date: 2022-07-15
• Subjects: Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2mh00639a
• Languages: English
• ISSNs: 2051-6347

Abstract

Abstract : With high molecular rigidity and planarity, the orange-red emitter SAF-2NP realized Φ PL and Θ ‖ of 99% and 85%, respectively. The optimal device demonstrated a maximum external quantum efficiency of 32.5% with an emission peak of 576 nm. Abstract : Simultaneous optimization of photoluminescence quantum yield ( Φ PL ) and horizontally oriented dipoles ( Θ ‖ ) is considerably challenging for orange and red thermally activated delayed fluorescence (TADF) emitters, due to the conflicts between enhancing molecular rigidity and improving molecular planarity. Herein, a novel orange-red TADF emitter 10-(dipyrido[3, 2- a :2′, 3′- c ]phenazin-11-yl)-10 H -spiro[acridine-9, 9′-fluorene] (SAF-2NP) was constructed with a donor–acceptor structure. The highly rigid donor and acceptor segments ensure the overall rigidity of the emitter. More importantly, the quasi-coplanar structure between the acceptor and the fluorene moiety in the donor unit enlarges the molecular plane without weakening rigidity. Consequently, SAF-2NP exhibited extremely high Φ PL and Θ ‖ of 99% and 85%, respectively. The optimal organic light-emitting diode using SAF-2NP as the emitter and 4, 4′-di(9 H -carbazol-9-yl)-1, 1′-biphenyl (CBP) as the host demonstrated an unparalleled external quantum efficiency of 32.5% and a power efficiency of 85.2 lm W −1 without any extra light extraction structure. This work provides a feasible strategy to establish efficient orange and red TADF emitters with both high rigidity and planarity.