Ultra-Sensitive All-Polymer Near-Infrared Photodetectors via Van der Waals Layered Triple Heterojunction.

All-polymer near-infrared (NIR) organic photodetectors (OPDs) offer exceptional stability and stretchability, making them highly promising for next-generation wearable electronics, biomedical sensing, and imaging applications. However, their practical implementation remains hindered by limitations such as low responsivity, high noise, and limited sensitivity, highlighting the critical challenge of optimizing the active layer structure to enhance device performance. In this study, we propose a van der Waals layered triple heterojunction (LTHJ) structure fabricated via water transfer printing (WTP) to reduce trap density, improve interfacial quality, optimize charge transport pathways, and enhance carrier dissociation and extraction efficiency. The LTHJ OPD exhibits simultaneously low noise and high responsivity, achieving ultra-low dark current (0.38 pA at -0.1 V; 2 pA at -2 V), an ultra-high switching ratio (>109), and a specific detectivity exceeding 1014 Jones. To the best of our knowledge, this performance represents one of the best-reported all-polymer OPDs to date, providing a novel strategy for developing high-performance polymer-based photodetectors. Furthermore, we demonstrate the potential of LTHJ OPDs in optical integrated sensing and communications (O-ISAC) by achieving obstacle-penetrating optical wireless communication (OWC) and long-distance misalignment photoplethysmography (PPG) signal monitoring, further underscoring their applicability in next-generation intelligent sensing and complex communication environments.