An Electron Acceptor With bis(Borondifluoride)‐8‐imidazodipyrromethene as the Core for Short‐Wavelength Infrared Photoresponse

Abstract

ABSTRACT Small‐molecule electron acceptors with donor–acceptor (D–A) structures have emerged as attractive materials for organic optoelectronics, yet achieving strong absorption in the short‐wavelength infrared (SWIR, 1000–3000 nm) region remains a fundamental challenge. Here, a resonant N—B←N unit, bis(borondifluoride)‐8‐imidazodipyrromethene (BIP), is introduced as a new electron‐deficient core for constructing D–A type SWIR acceptors. Incorporation of the BIP unit induces a pronounced bathochromic shift of 255 nm and affords an ultranarrow optical bandgap of 0.86 eV, with thin‐film absorption extending to 1450 nm. The resulting acceptor, BIP‐M1, exhibits a high molar extinction coefficient of 3.8 × 10 5 M − 1 cm − 1 and an exceptionally small Stokes shift of 0.054 eV, indicative of its strong SWIR absorption capability and suppressed nonradiative losses. Photodiode‐type organic photodetectors based on BIP‐M1 enable sensitive photoresponse over a broad spectral range from 300 to 1400 nm, delivering a responsivity of 0.18 A W − 1 and a specific detectivity of 3.93 × 10 11 Jones at 1200 nm, together with an ultralow Urbach energy of 19.19 meV. This study identifies resonant N—B←N units as powerful structural motifs for small bandgap molecular design and establishes BIP‐based small molecular acceptors as a promising platform for next‐generation SWIR optoelectronics.