Red-Emitting Thermally Activated Delayed Fluorescence Polymers with Poly(fluorene-co-3,3′-dimethyl diphenyl ether) as the Backbone

Abstract

A series of red-emitting thermally activated delayed fluorescence (TADF) polymers have been designed and synthesized based on poly(fluorene-co-3,3′-dimethyl diphenyl ether) (PFDMPE) as the backbone. Compared with polyfluorene (PF, 2.16 eV), the introduction of 3,3′-dimethyl diphenyl ether into the main chain of PFDMPE leads to the increased triplet energy of 2.58 eV, which is higher enough than the tethered red TADF guest (2.13 eV) to prevent the unwanted triplet energy back-transfer. Meanwhile, there is a good overlap between the absorption spectrum of the red guest and the photoluminescence (PL) spectrum of the polymeric host, ensuring the efficient energy transfer from host to guest. Consequently, the resultant polymers PFDMPE-R01 to PFDMPE-R10 in solid states show obvious red TADF properties with delayed fluorescence lifetimes of 126–191 μs and PL quantum yields of 0.18–0.55. Among them, PFDMPE-R05 obtains the best device performance, revealing a bright red electroluminescence peaked at 606 nm and a p...