Dielectric Interlayer Engineering Enables Functional Separation in Organic Phototransistors for Broadband...

Interfacial carrier transfer and electrostatic coupling critically govern the photoresponse of organic phototransistors (OPTs), yet direct electronic coupling between photoactive and transport semiconductors often entangles light harvesting, photogating, and field-effect transport. Here, we report a dielectric-interlayer-engineered Functionally Separated Architecture (FSA) in which a PMMA layer is inserted between a buried photoactive semiconductor and a high-mobility C8-BTBT transport channel. The dielectric interlayer suppresses direct interlayer carrier transport while retaining efficient capacitive electrostatic coupling. This interfacial configuration allows photogenerated charges accumulating in the buried photoactive layer to remotely gate the C8-BTBT channel while minimizing perturbation of its transport characteristics. The optimized D18-based FSA device exhibits stable transfer characteristics together with a photosensitivity of 1.5 × 104, a responsivity of 2.4 × 103 A W-1, and a shot-noise-limited specific detectivity of 6.2 × 1014 Jones under 520 nm illumination. Incorporating a D18:Y6 bulk heterojunction further extends the spectral response into the near-infrared region, achieving a photosensitivity of 4.7 × 105, a responsivity of 7.6 × 103 A W-1, and a shot-noise-limited specific detectivity of 4.4 × 1016 Jones under 850 nm illumination at 10.76 μW cm-2. The architecture is further validated with multiple polymer semiconductors, while its gate-programmable photoresponse supports multispectral edge extraction and device-constrained visual recognition. These results establish dielectric-interlayer-mediated electrostatic coupling as an interface design strategy for integrating photodetection, stable charge transport, and in-sensor visual processing in organic optoelectronic devices.