From a fluorescent chromophore in solution to an efficient emitter in the solid state.

Polycyclic aromatic hydrocarbons (PAHs) normally exhibit efficient fluorescence in dilute solutions, whereas their emission is significantly quenched in the aggregated state due to the formation of π-aggregates/excimers. The rigid and planar structure of PAHs plays a positive role in terms of fluorescence in solution but a negative one in the aggregated state. To bestow PAHs a luminescent ability in the solid state, we constructed a non-coplanar PAH-substituted ethene. By using the planar PAH fluoranthene as a building block, a highly efficient solid-state emitter with a fluorescence quantum efficiency of unity in the aggregated state was obtained. OLEDs with contain the molecule as an emitter reach a luminance up to 20 520 cd m(-2) and an efficiency of 10 cd A(-1).