Suppressing aggregation induced quenching in anthracene based conjugated polymers

Abstract

Anthracene is a highly valuable building block for luminescent conjugated polymers, particularly when a large singlet-triplet energy gap (ΔEST) is desired. Unfortunately, the extended π 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, ΦF) on going from solution to the solid state is especially common, represented in terms of a low ΦR (ΦR = ΦF film/ΦF 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 (ΦR ∼ 1, ΦF film ∼ 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.