The development of luminescent organic radicals has resulted in materials with excellent optical properties for near-infrared (NIR) emission. Applications of light generation in this range span from bioimaging to surveillance. Whilst the unpaired electron arrangements of radicals enable efficient radiative transitions within the doublet-spin manifold in organic light-emitting diodes (OLEDs), their performance is limited by non-radiative pathways introduced in electroluminescence. Here, we present a host:guest design for OLEDs that exploits energy transfer with demonstration of up to 9.6% external quantum efficiency (EQE) for 800 nm emission. The tris(2,4,6-trichlorophenyl)methyl-triphenylamine (TTM-TPA) radical guest is energy-matched to the triplet state in a charge-transporting anthracene-derivative host. We show from optical spectroscopy and quantum-chemical modelling that reversible host-guest triplet-doublet energy transfer allows efficient harvesting of host triplet excitons.
@article{arxiv.2308.02355,
title = {Efficient near-infrared organic light-emitting diodes with emission from spin doublet excitons},
author = {Hwan-Hee Cho and Sebastian Gorgon and Giacomo Londi and Samuele Giannini and Changsoon Cho and Pratyush Ghosh and Claire Tonnelé and David Casanova and Yoann Olivier and Feng Li and David Beljonne and Neil C. Greenham and Richard H. Friend and Emrys W. Evans},
journal= {arXiv preprint arXiv:2308.02355},
year = {2023}
}