Backbone modulation of thermally activated delayed fluorescence polymers for efficient orange-red emission in solution-processed OLEDs

Abstract

Thermally activated delayed fluorescence (TADF) enables near-unity internal quantum efficiency by harvesting triplet excitons via reverse intersystem crossing, but designing orange-red TADF polymers with high radiative rates and suppressed non-radiative loss remains challenging. Herein, design of orange-red TADF polymers via backbone engineering that tunes excited-state energies and energy-transfer pathways is reported. Carbazole and dibenzofuran (DBF) units are incorporated into the polymer backbones with various loadings of a naphthalimide–dimethylacridine unit. Altering DBF linkage (3,7- vs. 2,8-) modulates the photophysical properties of the polymer, enhancing energy transfer and exciton migration while reducing non-radiative decay. The polymer pNAI-DBF3705 exhibits a photoluminescence quantum yield of 78% and an accelerated reverse intersystem crossing rate of 8.76 × 10⁵ s⁻¹. Solution-processed OLEDs based on pNAI-DBF3705 deliver a maximum external quantum efficiency of 10% and improved operational stability at high driving voltages. These results highlight backbone engineering as an effective strategy to optimize excited-state dynamics in TADF polymers for high-performance, solution-processable orange-red OLEDs.