Multi-resonance TADF conjugated polymers with high rate constant of reverse intersystem crossing exceeding 10⁶ s⁻¹ for highly efficient solution-processible OLEDs

Due to the sole short-range charge transfer (SRCT) interaction within the multi-resonance (MR) emitting moiety, MR-thermally activated delayed fluorescence (MR-TADF) conjugated polymers generally exhibit long delayed fluorescence lifetimes (τ_Ds) and low rate constants of reverse intersystem crossing (k_RISCs) from triplet to singlet states. Consequently, the OLED devices based on these polymers often suffer from large efficiency roll-off due to the annihilation of the majority of triplet excitons. Herein, we propose a feasible strategy to construct MR-TADF conjugated polymers with short τ_Ds and high k_RISCs by introducing long-range charge transfer (LRCT) interaction into polymers. Owing to the SRCT/LRCT-hybrid emission, these synthesized polymers exhibit short τ_Ds of around 1 μs and high k_RISCs exceeding 10⁶ s⁻¹. The resulting solution-processible OLED devices achieve a maximum external quantum efficiency (EQE) of 17.7% with emission peak at 503 nm, and EQEs of near 15% and 10% are maintained at 100 and 500 cd m⁻², respectively, which represent the lowest EQE roll-off among MR-TADF polymer-based OLEDs to date.