Highly Sensitive Broadband Photodetectors Based on Donor-Acceptor 2D Conjugated Coordination Polymers

Two-dimensional (2D) semiconductors are highly desirable for broadband photodetection but are often constrained by their limited optical absorption and inefficient exciton dissociation. In this study, we report a donor-acceptor-engineered 2D conjugated coordination polymer (c-CP), Ni-TABQ (TABQ = tetraaminobenzoquinone), as a narrow-bandgap semiconductor. The TABQ ligands integrate electron-rich amino donors and electron-deficient quinone carbonyl acceptors within the same molecular backbone, endowing the Ni-TABQ lattice with strong intramolecular charge-transfer absorption and a built-in driving force for charge separation. Benefiting from strong broadband absorption and high charge-carrier mobility, the vapor-phase-grown Ni-TABQ thin films enable photodetection from 350 to 1400 nm under a 3 V bias, with a measurable response tail above 1150 nm, further achieving a responsivity of up to 3.1 A W^-1, a specific detectivity of up to 6.58 × 10¹⁰ Jones (625 nm at ∼85 µW cm^-2), and a response time of ∼206 µs, while maintaining stable operation at 3 V over 8500 s of continuous cycling. These metrics compare favorably with state-of-the-art broadband photodetectors based on standalone 2D materials, establishing donor-acceptor molecular engineering within the 2D metal-organic lattice as an effective strategy for advancing high-performance 2D optoelectronic devices.