O-B(F)←N Functionalized Copolymers with Delayed Fluorescence and P-Type Semiconducting Characteristics

Conjugated polymers with integrating properties of delayed fluorescence and photovoltaic responses simultaneously are scarcely reported due to the generally contradictory requirements for molecular structures to achieve the two properties. Herein, an O-B(F)←N functionalized fused unit (M) with multiple resonance features, small energy gap between lowest singlet excited state (S₁) and triplet excited state (T₁) (ΔE_ST = 0.23 eV), and delayed fluorescence (τ_D = 0.75 µs), is designed. Selecting three benzodithiophene (BDT) derivatives as co-units to copolymerize with M, leading to a series of O-B(F)←N embedded polymers also maintaining delayed fluorescence (τ_D = 0.4-0.5 µs). Moreover, p-type semiconductor characteristics are tested for these polymers with hole mobilities in the range of 10^-6-10^-5 cm²/Vs. Devices with obviously photovoltaic responses are prepared using these polymers as donors and Y6 as the acceptor, affording a preliminary efficiency of 5.05%. This work successfully demonstrates an effective strategy to design conjugated polymers with integrating properties of delayed fluorescence and photovoltaic performance simultaneously by introducing O-B(F)←N functional groups to polymer backbones.