High-efficiency circularly polarized emission from liquid-crystalline platinum complexes

Abstract

Realizing both a high emission efficiency and luminescence dissymmetry factor (glum) in circularly polarized solution processable organic light-emitting diodes (CP-OLEDs) remains a significant challenge. In this contribution, two chiral phosphorescent liquid crystals based on cyclometalated platinum complexes are prepared, in which the chiral s-2-methyl-1‑butyl group is introduced into the cyclometalating ligand and the mesogenic fragment is attached to the periphery of the ancillary ligand. The platinum complexes exhibit both smectic and chiral nematic phases as evidenced by polarized optical microscopy, differential scanning calorimetry and small-angle X-ray diffraction. Remarkably, a high photoluminescent quantum efficiency of over 78% and clear circularly polarized luminescent signal with gPL of about 10–2 are observed for the complexes. Further, solution-processed CP-OLEDs show maximum external quantum efficiencies (EQE) of over 15% and strong circularly polarized electroluminescent signals with a gEL ≈ 10–2. This research demonstrates that both liquid crystallinity and the number of chiral centers play key roles in improving the chiroptical property, paving the way for a new approach for the design of high-efficiency CPL emitters.

Metadata

Item Type:	Article
Authors/Creators:	Fan, Peng Fang, Zhou Wang, Shengyue Dong, Qiwei Xiao, Chen McEllin, Alice J. Bruce, Duncan W. https://orcid.org/0000-0002-1365-2222 Zhu, Weiguo Wang, Yafei
Copyright, Publisher and Additional Information:	Funding Information: The authors thank Professor Pengfei Duan, National Center for Nanoscience and Technology (NCNST), for measuring chiraloptical property and Dr Stephen Cowling, University of York, for collecting the small-angle X-ray data for complex s-Pt2. Financial support was from the National Natural Science Foundation of China (Nos. 51773021, 51911530197, 51473140), the Royal Society (IEC/NSFC/181139) and the National Natural Science Foundation of China (Nos. 51911530197 and 51773021) for an International Exchange Award (D.W. Bruce and Y. Wang) Six talent peaks project in Jiangsu Province (XCL-102), Natural Science Fund for Colleges and Universities in Jiangsu Province (No. 19KJA430002), and Key technological tasks in Anhui Province (JB20007). The authors also would like to thank Analysis and Testing Center, NERC Biomass of Changzhou University for their help on NMR measurements. Publisher Copyright: © 2023 Published by Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy.
Keywords:	Circularly polarized emission,Liquid-crystalline,Organic light-emitting diodes,Platinum complex
Dates:	Published: June 2023 Published (online): 7 April 2023 Accepted: 13 October 2022
Institution:	The University of York
Academic Units:	The University of York > Faculty of Sciences (York) > Chemistry (York)
Funding Information:	Funder Grant number THE ROYAL SOCIETY IEC\NSFC\181139
Depositing User:	Pure (York)
Date Deposited:	26 Apr 2023 07:30
Last Modified:	16 Oct 2024 19:10
Published Version:	https://doi.org/10.1016/j.cclet.2022.107934
Status:	Published
Refereed:	Yes
Identification Number:	10.1016/j.cclet.2022.107934
Related URLs:	http://www.scopus.com/inward/record.url?...
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:198602

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High-efficiency circularly polarized emission from liquid-crystalline platinum complexes

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