Year: 2025
Type: article
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, a new class of synthetically accessible molecules with quartet-derived luminescence is demonstrated, 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. A set of design rules is established by tuning the energetics in a series of compounds based on a naphthalimide (NAI) core. Generation of quartet states is observed and the strength of radical-triplet exchange is measured. 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.
Source: Advanced Materials
Institutions: University of Cambridge, University of Oxford, Aalto University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $6,070
Awards: G1167221005, G157799150, G1836445909, G1991678457, Polymer Radicals as doublet emitters for Organic Light-Emitting Diodes, Organic RADIcals as electroCHEMical and photoCHEMical energy materials (RADICHEM2), G3571472436, G3958972402, G434337789, Augmenting Oxford's Centre for Advanced Electron Spin Resonance with a Bruker Elexsys E580 X/Q-band pulsed ESR spectrometer, G680116334, EPSRC Core Equipment Award 2020 - University of Oxford, G8533033097, G8813462486
OpenAlex ID: W4410414043