Single-molecule white organic light-emitting diodes based on dual-conformation diindolophenthiazine derivatives

In this study, two isomers BP1 and BP2, featuring diindolophenthiazine as the donor and benzophenone as the acceptor, are designed and synthesized for the first time. Both compounds exhibit dual conformations and thus dual emissions of fluorescence and thermally activated delayed fluorescence in films to achieve single molecular white-light emissions. Owing to the dual conformations and the changes of their corresponding compositions in amorphous and crystalline states, machanochromism is observed in both compounds. Additionally, white photoluminescence with Commission Internationale de L’Eclairage (CIE) coordinates of (0.31, 0.33) are achieved for BP2-doped films. Furthermore, solution-processed single-molecule white organic light-emitting diodes are also successfully developed based on BP2 as the solely emitter, demonstrating an external quantum efficiency of 2.61% at CIE coordinates of (0.33, 0.36).