Theoretical study on the light-emitting mechanism of circularly polarized luminescence molecules with both thermally activated delayed fluorescence and aggregation-induced emission

Abstract

Circularly polarized luminescence molecules with both thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) have been reported recently and are thought as potential candidates for circular polarized organic light-emitting diodes. Since the study of these kinds of systems is quite limited, it is of great importance to reveal the relationship between the geometry and the light-emitting mechanism. In this paper, the TADF and AIE mechanisms were studied based on the study of a series of binaphthalene-containing luminogenic enantiomers in both toluene and solid phases. It was found that there was no influence on the light-emitting properties of enantiomers except for the electronic circular dichroism (ECD). The radiative rates for both molecules were enhanced in the solid phase, while the non-radiative rates were significantly suppressed. Both factors can induce the AIE phenomenon. Based on the calculation of the decay rates and adiabatic excitation energy of the excited states, we found that the TADF mechanisms of the two molecules were different. One is realized by the up-conversion process between S₁ and T₁, while a two-step process is involved for the other. Our theoretical research successfully elucidates the experimental measurement and illustrates the AIE and TADF mechanism, which could provide valuable insights for the design of highly efficient CPL emitters.