Excited state dynamics of intramolecular charge transfer excited state in thermally activated delayed fluorescence carbazole dendrimer

Organic light-emitting diodes (OLEDs) using dendrimers as emitting layers are gathering attention due to their ability of precise molecular structuring. Carbazole dendrimers have been utilized in luminescent devices demonstrating thermally activated delayed fluorescence (TADF), which efficiently converts non-emissive triplet states to emissive singlet states, enhancing OLED performance. Our research examined triazine-cored carbazole TADF dendrimers with three generations, assessing their photofunctional properties through time-resolved photoluminescence and transient absorption spectroscopy. We revealed significant generation-dependent charge-transfer characteristics, with higher generations showing enhanced charge-transfer character in the singlet excited state. On the contrary, while the transient absorption spectra of the singlet excited state were modified sensitively by elongation of the dendron, those of the triplet excited state were insensitive to the generation. This study underscores the importance of molecular design in dendrimers for optimizing electronic properties, providing insights into their unique photophysical behaviors, and potentially guiding future developments in OLED technology.