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Electroabsorption spectroscopy as a tool to probe charge-transfer and state mixing in thermally-activated delayed fluorescence emitters.

De Sa Pereira, Daniel and Menelaou, Christopher and Danos, Andrew and Marian, Christel Maria and Monkman, Andrew P. (2019) 'Electroabsorption spectroscopy as a tool to probe charge-transfer and state mixing in thermally-activated delayed fluorescence emitters.', Journal of physical chemistry letters., 10 (12). pp. 3205-3211.


Solid-state electroabsorption is demonstrated as a powerful tool to probe the charge-transfer (CT) character and state mixing in the low energy optical transitions of two structurally similar thermally-activated delayed fluorescent (TADF) materials with divergent photophysical and device performances. The Liptay model is used to fit differentials of the low energy absorption bands to the measured electroabsorption spectra, with both emitters showing CT characteristics and large changes of dipole moments on excitation despite the associated absorption bands appearing structured. High electric fields then reveal transfer of oscillator strength to a state close to the CT in the better performing molecule. With supporting TDDFT-TDA and DFT/MRCI calculations, this state showed ππ* characteristics of a local acceptor triplet that strongly mixes with the σπ* of the CT. The emitter with poor TADF performance showed no evidence of such mixing.

Item Type:Article
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Publisher statement:This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
Date accepted:21 May 2019
Date deposited:24 May 2019
Date of first online publication:22 May 2019
Date first made open access:No date available

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