Thermally activated delayed fluorescence polymers with well-defined structures to explore structure–performance correlation

Abstract

Thermally activated delayed fluorescence (TADF) polymers are the ideal emission layers for solution-processed organic light-emitting diodes (OLEDs). However, most existing TADF polymers are characterized by random copolymer architectures, formed via multi-monomer copolymerization. The irregular distribution of the TADF chromophore may lead to ambiguous structure–performance correlation and represents a substantial challenge in achieving device stability. Herein, a series of structurally well-defined TADF polymers, PyCzABP, were successfully synthesized by alternating copolymerization of TADF-based bromide monomers and oligomeric carbazole units, where y represents the number of carbazole rings. Accordingly, TADF units are spatially separated by the oligomeric carbazole segment from P1CzABP to P5CzABP. Upon increasing y from 1 to 5, the photoluminescence quantum yields of the polymers gradually increase from 62% to 89% with an almost identical emissive wavelength of 543 nm except for P1CzABP. Moreover, the non-doped and solution-processed OLED with P5CzABP achieves a maximum external quantum efficiency of 19.7% and a turn-on voltage of 2.5 V, which are superior to those of random polymers with similar TADF units.