Polymorphism dependent triplet-involved emissions of a pure organic luminogen

Abstract

Polymorphism has been frequently used in tuning the singlet emissions of pure organic dyes. The modulation of triplet-involved emissions, particularly room temperature phosphorescence (RTP), however, is scarcely reported. Herein, polymorphism is reported to tune the triplet-involved emissions of 2CZBZL, a newly designed pure organic luminogen consisting of twisted benzil and two planar carbazole moieties. Other than the conventional modulation through changing molecular conformation and packing, vibration can also finely tune the triplet-involved emissions. Besides prompt fluorescence (PF), polymorph B with relatively extended conformation emits thermally activated delayed fluorescence (TADF), whereas the others (A, C–E) with similarly more twisted conformations generate predominant RTP or simultaneous DF and RTP. These results demonstrate the fascinating chance to regulate the triplet-involved emissions through controlling conformation and vibration.