Molecular design for organic luminogens with efficient emission in solution and solid-state

Design and synthesis of organic luminogens with efficient emission in both solution and solid-state (namely, dual-state emission: DSE) still face enormous challenges, a majority of luminescent compounds are always either aggregation-caused quenching or aggregation-induced emission luminogens. The development of dual-state emissive materials is extremely desirable for advanced applications. However, up to now, how to design this kind of materials remains a big challenge. Thus, a further in-depth understanding of the dual-state emission still needs to be established. In this work, a rational molecular design strategy has been presented based on triphenylamine via theoretical calculation and practical verification. First, steric hindrance effect of triphenylamine molecule can render the intramolecular rotation restricted in solution state, which could reduce the non-radiative transition; second, the twisted structure prevents or alleviates detrimental close molecular packing in the solid state; third, rational chemical modification forbids or inhibits the Sn – Tn intersystem crossing, which prevents the formation of triplet excitons and decrease the non-radiative transition rate. Once the above conditions are satisfied, the triphenylamine derivatives can exhibit bright emission in both solution and solid-state. This efficient strategy has been strongly confirmed by TPA-BP, TPA-BT, TPA-BBT and several molecules previously reported. We believe that this work will help to design novel luminescent materials with efficient emission in both solution and solid-state, which is of benefit to organic light-emitting diodes (OLEDs), chemical sensors, smart optoelectronic materials, and other high-tech areas.