Molecular and Optical‐Field Engineering of BODIPY‐Based Donor Polymers for Semitransparent Near‐Infrared Organic Photodetectors

ABSTRACT Developing semitransparent near‐infrared organic photodetectors requires donor materials that simultaneously combine strong NIR absorption, high visible transparency at the device level, low electronic noise, and compatibility with transparent device architectures. Here, we develop a BODIPY‐based donor polymer, PBODIPY‐T, and investigate its semitransparent photodetectors using PBODIPY‐DPP as a structurally related reference. Composition optimization and thickness‐dependent optical simulations guide the device design. A representative PBODIPY‐T: PC 61 BM device with a 1:1 donor‐to‐acceptor ratio achieves an average visible transmittance of 58.3%, an external quantum efficiency of 25.3% at 820 nm, a maximum specific detectivity of 2.2 × 10 12 Jones, and a ‐3 dB bandwidth of 79 kHz. Transfer‐matrix simulations and measurements of devices with different active‐layer thicknesses support the selection of 55 nm as a practical compromise between NIR response and electrical reliability. The optimized composition combines relatively balanced carrier mobilities with low measured noise and favorable photodetection performance. Device reproducibility is evaluated using ten independently fabricated devices. This semitransparent platform further enables optical communication, spectral demultiplexing, multispectral imaging, and flexible fingertip photoplethysmography. These results establish PBODIPY‐T as a donor platform for semitransparent NIR detection.