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Fast Transfer of Triplet to Doublet Excitons from Organometallic Host to Organic Radical Semiconductors

Qinying Gu, Sebastian Gorgon, Alexander S. Romanov, Feng Li, Richard H. Friend, Emrys Evans Orcid Logo

Advanced Materials

Swansea University Author: Emrys Evans Orcid Logo

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DOI (Published version): 10.1002/adma.202402790

Abstract

Spin triplet exciton formation sets limits on technologies using organic semiconductors that are confined to singlet-triplet photophysics. In contrast, excitations in the spin doublet manifold in organic radical semiconductors can show efficient luminescence. Here we explore the dynamics of the spin...

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Published in: Advanced Materials
ISSN: 0935-9648 1521-4095
Published: Wiley 2024
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa66573
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Abstract: Spin triplet exciton formation sets limits on technologies using organic semiconductors that are confined to singlet-triplet photophysics. In contrast, excitations in the spin doublet manifold in organic radical semiconductors can show efficient luminescence. Here we explore the dynamics of the spin allowed process of intermolecular energy transfer from triplet to doublet excitons. We employ a carbene-metal-amide (CMA-CF3) as a model triplet donor host, since following photoexcitation it undergoes extremely fast intersystem crossing to set up a population of triplet excitons within 4 ps. This enables a foundational study for tracking energy transfer from triplets to a model radical semiconductor, TTM-3PCz. Over 74% of all radical luminescence originates from the triplet channel in this system under photoexcitation. We find that intermolecular triplet-to-doublet energy transfer can occur directly and rapidly, with 12% of triplet excitons transferring already on sub-ns timescales. This enhanced triplet harvesting mechanism is utilised in efficient near-infrared organic light-emitting diodes, which can be extended to other opto-electronic and -spintronic technologies by radical-based spin control in molecular semiconductors.
Keywords: doublet emission; exciton management; OLEDs; photophysics; radical materials
College: Faculty of Science and Engineering
Funders: Cambridge Trust China Scholarship Council - 201808060075 Engineering and Physical Sciences Research Council - EP/M005143/1 Engineering and Physical Sciences Research Council - EP/W018519/1 Engineering and Physical Sciences Research Council - EP/S022953/1 H2020 European Research Council - 101020167 National Natural Science Foundation of China - 2019TD-33 National Natural Science Foundation of China - 51925303 Royal Society - URF\R1\201300 Simons Foundation - 601946