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arXiv · 2411.18112

Open-shell TADF: Quartet-derived luminescence with dark radicals

Sebastian Gorgon·Petri Murto·Daniel G. Congrave·Lujo Matasovic·Andrew D. Bond·William K. Myers·Hugo Bronstein·Richard H. Friend
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Abstract

High-spin states in organic molecules offer promising tuneability for quantum technologies. Photogenerated quartet excitons are an extensively studied platform, but their applications are limited by the absence of optical read-out via luminescence. Here we demonstrate a new class of synthetically accessible molecules with quartet-derived luminescence, formed by appending a non-luminescent TEMPO radical to Thermally Activated Delayed Fluorescence (TADF) chromophores previously used in OLEDs. The low singlet-triplet energy gap of the chromophore opens a luminescence channel from radical-triplet coupled states. We establish a set of design rules by tuning the energetics in a series of compounds based on a naphthalimide (NAI) core. We observe generation of quartet states and measure the strength of radical-triplet exchange (0.7 GHz). In DMAC-TEMPO, up to 72% of detected photons emerge after reverse intersystem crossing from the quartet state repopulates the state with singlet character. This design strategy does not rely on a luminescent radical to provide an emission pathway from the high-spin state. The large library of TADF chromophores promises a greater pallet of achievable emission colours.

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Sebastian Gorgon, Petri Murto, Daniel G. Congrave, Lujo Matasovic, Andrew D. Bond, William K. Myers, Hugo Bronstein, Richard H. Friend. 2024-11-27. Open-shell TADF: Quartet-derived luminescence with dark radicals. https://doi.org/10.1002/adma.202501164

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