Donor–Acceptor Conjugated Polymers for Single-Component Near-Infrared II Organic Phototransistors with Ultrahigh Photoresponsivity

The design of donor–acceptor (D–A) conjugated polymers with narrow bandgaps remains a big challenge for achieving high-performance near-infrared (NIR) phototransistors. Herein, we report a novel D–A conjugated polymer (denoted as TBOPV-DT) based on a thiophene-fused benzodifurandione-based oligo(p-phenylenevinylene) (TBOPV) acceptor in conjugation with a 3,3′-dialkoxy-2,2′-dithiophene (DT) donor. Benefiting from the alkoxylation of the donor units, the TBOPV-DT conjugated polymer exhibits broad second NIR absorption and a narrow bandgap of 0.65 eV. When being used as the channel material in field-effect transistors, the TBOPV-DT conjugated polymer shows p-type semiconducting behavior with a hole mobility of 0.16 cm² V^–1 s^–1. Besides, the resulting single-component polymer phototransistor displays ultrahigh sensitivity to a broad range of wavelengths (850–1450 nm) and a record-high photoresponsivity of 1.9 × 10⁵ A W^–1. Moreover, the fast rise and decay response times of 53 and 317 ms, respectively, are comparable to those of state-of-the-art two-dimensional materials. This work sheds light on designing new narrow-bandgap D–A conjugated polymers with molecular precision and paves the way for the development of future high-performance optoelectronics.