Oxygen-Positional 2D Side-Chain Engineering of n-Type Acceptors for Record >90% Near-Infrared External Quantum Efficiency in Broadband Perovskite–Organic Photodetectors

Abstract

Side-chain engineering, a powerful approach to tune molecular properties and charge transport, has to the best of our knowledge never been applied to n-type semiconductors in perovskite-organic heterojunction photodetectors (POH-PDs). Herein, we report two n-type non-fullerene acceptors (Y1PhO and Y2PhO), featuring 2D-conjugated outer side chains in which a single oxygen atom is incorporated at distinct positions. The oxygen-position-tuned 2D-conjugated chains afford precise control over bulk photophysics and buried-interface energetics in POH-PDs. Relative to the benchmark non-fullerene acceptor Y6, both molecules exhibit larger dipole moments, higher dielectric constants, and up-shifted frontier-orbital energies. The relaxed backbone planarity serves to inhibit over-aggregation, yielding smoother bulk-heterojunction blend films and superior interfacial coupling with CsFA perovskite layer, most notably in PM6:Y2PhO blend. As a consequence, the Y2PhO-based POH-PD delivers a near-infrared external quantum efficiency exceeding 90%−the highest value reported for solution-processable broadband PDs to date− together with a high responsivity of 0.623 A W−1, shot-noise-limited and noise-based detectivities of 7.05 × 1012 and 1.43 × 1011 Jones, respectively, at 830 nm, and a linear dynamic range of 109.1 dB. These performance metrics significantly surpass those of the Y6-based counterpart, establishing oxygen-position engineering as a compelling molecular design strategy for next-generation, ultrahigh-sensitivity broadband photodetectors.