Functionalized tails influence photoluminescence emissions for advanced applications in the fiel of time-resolved information input and erasure

Abstract

The study of small organic molecules that have different molecular structures with the same luminescent core, which produces fluorescence, phosphorescence or delayed fluorescence, is fascinating. Of course, the regulation of elaborate chemical structures is a reliable way to achieve these emission properties. In this study, five carbazole derivatives with different functional groups were obtained via C–N coupling reactions: Cz–C₈, Cz–C₈–Br, Cz–C₈–OH, Cz–C₈–Tu and Cz–C₇–COOH. Our results reveal that small differences in functionalized tail groups can produce a huge contrast in photoluminescence behavior. Obviously, more polar tails, such as −Tu and −COOH, contribute more to high-performance organic room temperature phosphorescent materials. The non-polar tail of –H favors delayed fluorescence, while the mid-polar group of –OH enables phosphorescence and delayed fluorescence in Cz–C₈–OH. These two different behaviors can be artificially modulated by external stimuli, such as photoactivation and thermal annealing. A study of the internal mechanism shows that intermolecular interactions and the molecular aggregation state are the main factors affecting the photoluminescence performance. Finally, advanced applications in the fields of data encryption, data storage, and anti-counterfeiting are illustrated using time-resolved techniques.