Emergent Acceptor Fibrillar Network Enable MHz‐Level Response in Solution‐Processed NIR‐SWIR Organic Photodetectors

Achieving fast photoresponse in solution‐processed organic photodetectors (OPDs), particularly in the near‐infrared (NIR) and short‐wave infrared (SWIR) regions, remains a longstanding challenge, due to intrinsically limited charge transport and processing‐induced morphological disorder. Here, we report a general morphological control strategy, a large‐scale acceptor‐rich fibrillar network, for significantly boosting the response speed of NIR OPDs without compromising detectivity. Driven by compositional demixing at high acceptor addition, the acceptor‐rich fibrillar morphology yields improved exciton dissociation and charge carrier transport, enabling cutoff frequencies of 1.05 MHz at 870 nm, 1.7 MHz at 1050 nm, and 722 kHz at 1200 nm across different blend systems. The practical potential of these fast‐response OPDs is further validated by high‐fidelity optical communication and infrared imaging. Our study establishes large‐scale acceptor fibrillar network as an effective and general morphological control guideline for developing high‐speed OPDs across the NIR‐SWIR spectral range.