Suppressing aggregation induced quenching in anthracene based conjugated polymers

Anthracene is a highly valuable building block for luminescent conjugated polymers, particularly when a large singlet-triplet energy gap (Delta E-ST) is desired. Unfortunately, the extended pi system of anthracene imparts a strong tendency for polymer aggregation, resulting in detrimental effects on its solid state photophysics. A large decrease in photoluminescence quantum yield (PLQY, phi(F)) on going from solution to the solid state is especially common, represented in terms of a low phi(R) (phi(R) = phi(F film)/phi(F sol.)). Significant and undesirable red-shifting of fluorescence in the solid state is also typical due to processes such as excimer formation. In this work a series of alkylene-encapsulated conjugated anthracene polymers is developed to overcome these challenging problems. We demonstrate a promising material which displays a good solid state PLQY that is effectively unchanged compared to solution measurements (phi(R) similar to 1, phi(F film) similar to 40%), alongside an identical PL 0-0 transition wavelength in solution and thin film. Such a direct transfer of luminescence properties from solution to the solid state is remarkable for a conjugated polymer and completely unprecedented for one based on anthracene.