Unique dual fluorescence emission in the solid state from a small molecule based on phenanthrocarbazole with an AIE luminogen as a single-molecule white-light emissive material

Abstract

Purely organic molecules with dual emissive properties have received increased attention in the last decade as they are now being utilized in practical optoelectronic, sensing and biomedical applications. We presented two new tetraphenylethylene- and triphenylethylene-substituted phenanthrocarbazoles (PCs) (PCTPE and PCTrPE) with different molecular geometries and crystal packings, resulting in distinct fluorescence emission in solution and the solid state. In particular, PCTrPE adopting a highly sterically crowded conformation showed dual fluorescence emission both in THF/water mixtures and the solid state with AIE characteristics. The two fluorophores in the molecule emitted their inherent emission profiles with no energy transfer. Combining the blue emission from the isolated PC unit and the longer-wavelength emission (green to orange-red) from the weak electronic interaction of PC and the triphenylethylene AIE luminogen gave rise to white-light emission without excimer emission. The WOLED fabricated with PCTrPE as a non-doped single molecule emitter exhibited good white color stability with a current efficiency of 1.02 cd A⁻¹, CIE(x, y) coordinates of (0.29, 0.34) and a color rendering index of 80. This finding reports the first example of a single molecule with dual fluorescence emission in the solid state with no emission from excimers and provides a new strategy for realizing single white-light-emitting molecules via a unique solid-state dual luminescence property from an AIE luminogen functionalized compound.