Synthesis and characterizations of new organic molecules luminescent for applications in lighting and bioimaging

In recent years, devices based on thermally activated delayed fluorescence (TADF) emitters have proven to be the most promising and efficient approach to convert dark triplet states into emissive singlet states. TADF materials are characterized by a small energy gap between the excited singlet state (S1) and the excited triplet state (T1), this gap called ΔEST is generally less than 0.2 eV. As with phosphorescent emitters, purely organic TADF emitters can recruit excitons from both singlet and triplet states for light emission and thus allow to construct OLED devices reaching 100% internal quantum efficiencies (IQE). An important advantage of these emitters is related with their organic molecular skeleton, thus avoiding the problems associated with the use of heavy metal-based organometallic complexes. Thanks to their unique photophysical properties, organic TADF materials are being studied for a wide range of domains, such as in organic light emitting diodes (OLEDs), solar cells, photocatalysis, etc. Furthermore, TADF-based materials have a unique advantage in some imaging techniques due to their longer life than promptly fluorescent materials. These organic compounds are particularly promising in bioimaging applications due to their low cytotoxicity compared to traditional compounds such as lanthanide complexes. In the course of this thesis, the synthesis and photophysical characterization of new organic TADF molecules was carried out, specifically new coumarin and spiro structures, candidates for the construction of new OLED and as non-toxic biomarkers with efficient emissions in the blue-green spectral region.