Abstract
Thermally activated delayed fluorescence (TADF) of 12C70 and 13C70 was observed up to 140 °C in a p-tert-butyldihomooxacalix[4]arene solid matrix, a temperature range significantly higher than that of previous TADF quantitative studies. An effective singlet–triplet energy gap of 29 kJ/mol and triplet formation quantum yields of 0.97 and 0.99 were measured for 12C70 and 13C70, respectively. The photophysical properties of the two fullerenes in this new matrix are comparable to those obtained in polystyrene at a lower temperature range. Calixarenes are proposed to be suitable matrices for high temperature TADF studies and applications.
Highlights
Activated delayed fluorescence (TADF) is a type of fluorescence emission displaying both singlet and triplet properties: the emission spectrum is like that of normal fluorescence, whereas the lifetime is close to that of phosphorescence [1,2]
The Thermally activated delayed fluorescence (TADF) of normal and C-13 enriched fullerene C70 up to 140 C using to 140 °C using p-tert-butyldihomooxacalix[4]arene (DHOC4)
This method is based on the measurement of the prompt fluorescence (PF) and delayed fluorescence (TADF) steady-state intensities, IPF and IDF, as a function of temperature, plotted according to ln
Summary
Activated delayed fluorescence (TADF) is a type of fluorescence emission displaying both singlet and triplet properties: the emission spectrum is like that of normal (prompt) fluorescence, whereas the lifetime is close to that of phosphorescence [1,2]. The S1 -T1 -S1 cycle can occur several times This mechanism is only operative for very low concentrations of molecular oxygen, otherwise the triplet state is quenched [1,2,3,4,5]. TADF is not observed in most fluorophores—e.g., aromatic hydrocarbons and derivatives—owing to the large singlet–triplet energy gap (∆EST > 0.45 eV), in comparison with kT [6]. It can be observed in some xanthene dyes and a few ketones and porphyrins [7,8,9]. Molecules 2018, 23, x FOR PEER REVIEW co-workers discovered the carbon-13 (C-13) isotope effect in luminescence (not observed before in before in any molecule), and in particular in triplet
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