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Inverting the Handedness of Circularly Polarized Luminescence from Light-Emitting Polymers Using Film Thickness

Lookup NU author(s): Dr Beth Laidlaw, Professor Thomas Penfold



This is the authors' accepted manuscript of an article that has been published in its final definitive form by American Chemical Society, 2019.

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The emission of circularly-polarized light is central to many applications, including data storage, quantum computation, biosensing, environmental monitoring and display technologies. An emerging method to induce (chiral) circularly-polarized (CP) electroluminescence from the active layer of polymer light emitting diodes (polymer OLEDs; PLEDs) involves blending achiral polymers with chiral small molecule additives, where the handedness/sign of the CP light is controlled by the absolute stereochemistry of the small molecule. Through the in-depth study of such a system we report an interesting chiroptical property: the ability to tune the sign of CP light as function of active layer thickness for a fixed enantiomer of the chiral additive. We demonstrate that it is possible to achieve both efficient (4.0 cd/A) and bright (8000 cd/m2) CP-PLEDs, with high dissymmetry of emission of both left handed (LH) and right handed (RH) light, depending on thickness (thin films, 110 nm: gEL = 0.51, thick films, 160 nm: gEL= −1.05, with the terms “thick” and “thin” representing the upper and lower limits of the thickness regime studied), for the same additive enantiomer. We propose that this arises due to an interplay between localized CP emission originating from molecular chirality and CP light amplification or inversion through a chiral medium. We link morphological, spectroscopic, and electronic characterization in thin films and devices with theoretical studies in an effort to determine the factors that underpin these observations. Through the control of active layer thickness and device architecture, this study provides insights into the mechanisms that result in CP luminescence from CP-PLEDs, opportunities in CP photonic device design, and demonstrate high performance CP-PLEDs.

Publication metadata

Author(s): Wan L, Wade J, Salerno F, Arteaga O, Laidlaw B, Wang X, Penfold T, Fuchter MJ, Campbell AJ

Publication type: Article

Publication status: Published

Journal: ACS Nano

Year: 2019

Volume: 13

Issue: 7

Pages: 8099-8105

Print publication date: 23/06/2019

Online publication date: 17/06/2019

Acceptance date: 14/06/2019

Date deposited: 19/06/2019

ISSN (print): 1936-0851

ISSN (electronic): 1936-086X

Publisher: American Chemical Society


DOI: 10.1021/acsnano.9b02940


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