Liquid-Crystalline Thermally Activated Delayed Fluorescence : Design, Synthesis, and Application in Solution-Processed Organic Light-Emitting Diodes

Abstract

Realizing both high efficiency and liquid crystallinity in one molecule remains a challenge in thermally activated delayed fluorescence (TADF) emission. Herein, two isomeric compounds- m-DPSAc-LC and p-DPSAc-LC with different connection positions between donor and acceptor moieties- were synthesized and characterized. Diphenylsulfone (DPS) was used as the acceptor, acridine (Ac) was used as the donor, and biphenyl derivatives (LC) were employed as the mesogenic group. Both compounds showed a smectic mesophase evidenced by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and temperature-dependent small-angle X-ray scattering (SAXS). The compound p-DPSAc-LC clearly exhibited thermally activated delayed fluorescence due to the much more distorted geometry, whereas m-DPSAc-LC showed simple fluorescence. Compared to the parent TADF molecules without appended mesogenic groups (DPS-Ac), these liquid-crystalline emitters possessed higher hole mobilities and improved device performance. The OLEDs fabricated via solution processing using the liquid-crystalline compound p-DPSAc showed a maximum external quantum efficiency of ∼15% and as such is the first example of a liquid-crystalline TADF material in an OLED device.

Metadata

Authors/Creators:

Zhu, Yuanyuan
Zeng, Songkun
Li, Bing
McEllin, Alice J.
Liao, Junxu
Fang, Zhou
Xiao, Chen
Bruce, Duncan W. https://orcid.org/0000-0002-1365-2222
Zhu, Weiguo
Wang, Yafei

Funding Information: Financial support was provided by the National Natural Science Foundation of China (Nos. 51773021, 51911530197) and the Six Talent Peaks project in Jiangsu Province (XCL-102). DWB and YW thank the Royal Society and the NSFC for an International Joint Project Grant, and AJM thanks the University of York for financial support. The NMR testing was provided by Analysis and Testing Center, NERC Biomass of Changzhou University. © 2022 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

Keywords:

acridine, diphenylsulfone, liquid crystal, solution-processable OLED, synthesis and properties, thermally activated delayed fluorescence

Dates: