Thermally activated delayed fluorescence (TADF) is an uncommon type of molecular fluorescence resulting from both singlet and triplet state properties: the emission spectrum is identical to that of normal (prompt) fluorescence, whereas the lifetime is close to that of phosphorescence [1]. In the TADF mechanism, after excitation and once the S1 state is reached, intersystem crossing (ISC) to the triplet manifold takes place, followed by a second ISC back to S1, from which fluorescence ensues. The S1-T1-S1 cycle can occur several times and is temperature dependent, however this mechanism is only operative for very low concentrations of molecular oxygen, otherwise the triplet state is quenched. Owing to the oxygen and temperature dependences, TADF can be used both in molecular thermometry and oxygen sensing [2]. In addition, TADF has also been used in the development of 3rd generation organic light-emitting diodes (OLEDs) [3,4]. In order to have an efficient TADF emission, several conditions are required. One of the most important requirements is a small value for the singlet-triplet energy gap (ΔEST). The design of new molecules for OLEDs has as the main goal a reduced ΔEST [5]. Herein, we use several methods of analysis to estimate the ΔEST of several molecules designed by us, having in mind the OLED application. In addition, further important parameters such as the singlet and triplet formation quantum yields and the phosphorescence lifetime, also important for TADF characterization, are also discussed.

Photophysical studies of molecules with thermally activated delayed fluorescence for application in organic light emitting diodes

254th National Meeting (2017)

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