# On the temperature dependence of the quenching by a few defects of TADF materials. Triplet versus Singlet FRET

Zhengyu Zhang, Arnaud Brosseau, Margaux Elie, Matthieu Hamel, Sylvain

Gaillard, Robert Bernard Pansu

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Zhengyu Zhang, Arnaud Brosseau, Margaux Elie, Matthieu Hamel, Sylvain Gaillard, et al.. On the temperature dependence of the quenching by a few defects of TADF materials. Triplet versus Singlet FRET. ICP 2017 - 28th International Conference on Photochemistry, University of Strasbourg, Jul 2017, Strasbourg, France. cea-04938719

HAL Id: cea-04938719

https://cea.hal.science/cea-04938719v1

Submitted on 10 Feb 2025

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# On the temperature dependence of the quenching by a few defects of TADF materials. Triplet versus Singlet FRET.

Zhengyu Zhang,ª Arnaud Brosseau,ª Margaux Elie,ᵇ Matthieu Hamel,ᶜ Sylvain Gaillard ᵇ and Robert B. Pansu.ª

E-mail : pansu@ppsm.ens-cachan.fr

Thermally Activated Delayed Fluorescence (TADF) molecules contribute to the light emission of an optoelectronic device from both their singlet and triplet states. But the quenching limits these benefits. In the case of cationic (NHC)Cu(I) complexes bearing 2,2'-dipyridylamine<fnref n="1" /> solids, we have studied the quenching mechanism, the exciton mobility and its energy transfer efficiency as a function of temperature. We can create defects in crystals of TADF molecules by a strong laser irradiation. The quenching efficiency by these defects depends on the temperature.

<figure><img src="image_3.png" /><figcaption>Figure 1 The decay rate of the unquenched population ● depends on temperature because of the Boltzmann equilibrium between the Singlet and Triplet states. From that an energy difference between the two states can be measure to be 10kJ/mol. Below 240°K, the quenching volume decreases with the Singlet state contribution.</figcaption></figure>

This is because the repartition between the singlet and triplet states depends on the temperature and the singlet state is more prone to quenching through the FRET. From the analysis of the decay curves, we show that the excitons are not mobile in the crystal. We also show that the quenching is through FRET. We show that the quenching is due to the small number (<3) of defects inside the quenching volume. Using a time resolved version of the Perrin quenching model,¹¹ we measure the average of this number that is reported on Fig.1.

**Funding:** http://www.agence-nationale-recherche.fr/?Projet=ANR-15-CE39-0006

<footnote>ª PPSM, UMR8531 & Inst. d'Alembert FR3242, CNRS / ENS Paris Saclay.</footnote>

<footnote>ᵇ LCMT, Normandie Université, CNRS, UMR 6507, 6, Bd. du Maréchal Juin, F-14050 Caen.</footnote>

<footnote>ᶜ CEA, LIST, Laboratoire Capteurs et Architectures Électroniques, F-91191 Gif-sur-Yvette).</footnote>

<footnote n="1">¹ M. Elie, et al., *ACS Appl Mater Interfaces*, **2016**, *8*, 14678-91.</footnote>

<footnote>ii L. Hartmann, et al., *ACS Nano*, **2012**, *6*, 9033–9041.</footnote>