Highly Red Emissive Conjugated Homopolymers Based on Double B←N Bridged Bipyridine Unit

Conjugated homopolymers based on six-member rings,e.g.,polyfluorene,always exhibit blue emission and conjugated homopolymers based on five-member rings,e.g.,polythiophene,can give red emission with low efficiency.In this work,we report a series of new conjugated homopolymers based on six-member rings with high-efficiency deep-red emission.The repeating units of the red light emitting homopolymers are double B←N bridged bipyridine(BNBP)with the boron atoms functionalized with diphenyl,borafluorene,and 2,7-di-tert-butyl-borafluorene groups,respectively.The relationship between the chemical structures and the opto-electronic properties of the monomers and the homopolymers has been systematically studied.The three polymers emit pure red light(λ_(max)=656 nm)or deep red light(λ_(max)=693 nm)with fluorescence quantum efficiency in solution higher than 60%.The polymers can be used as the emitters in solution-processed organic light-emitting diodes with red emission and decent device performance.This work indicates a new strategy to design highly efficient light emitting conjugated polymers.