Molecular‐Device Co‐Engineering of Ultra‐Low Dark Current SWIR Organic Photodetectors for High‐Quality Blood‐Pressure Monitoring and Optical Communication

Abstract The limited noise‐responsivity balance in Short‐wave infrared (SWIR) organic photodetectors (OPDs) restricts their biomedical and optoelectronic applications. In this study, this challenge is addressed through molecular‐device co‐engineering by designing two fluorinated narrow‐bandgap non‐fullerene acceptors (BTT‐DTPn and BTT‐DTPn‐2F) coupled with solvent vapor annealing (SVA), achieving low noise and high detectivity in SWIR OPDs. The optimized devices based on BTT‐DTPn‐2F, which features enhance π–π stacking due to terminal fluorination, extend its absorption capability to 1300 nm. Under −0.1 V bias, the SVA‐processed BTT‐DTPn‐2F devices demonstrate an ultra‐low dark current ( J d ) of 4.93 × 10 −8 A cm −2 and exhibit a suppressed trap density of states (tDOS) reduced by an order of magnitude, achieving a shot‐noise limited detectivity () of 7.19 × 10 11 Jones at 1200 nm. The synergy of molecular design and post‐processing enables an ultra‐fast response time (1.44/1.20 µs rise/fall) and a record‐high −3 dB cutoff frequency ( f −3 dB ) of 648 kHz, demonstrating remarkable performance for SWIR OPDs. These advancements facilitate two groundbreaking applications: deep‐tissue photoplethysmography (PPG) for cuff‐less blood pressure monitoring and high‐speed, real‐time SWIR optical communication. This methodology presents a general strategy to harmonize molecular design with device fabrication in SWIR OPDs.