Non-Contact Dipole Moment Electric Modulation Achieving High Performance Near-Infrared Organic Photodetectors

Near-infrared (NIR) detectors, serving as critical technological nodes bridging microscopic molecular recognition and macroscopic intelligent perception, meet the demands of cutting-edge technologies such as multispectral imaging. Organic semiconductor materials demonstrate unique advantages for NIR organic photodetectors (OPDs) due to their precisely tunable bandgaps, solution processability, flexibility compatibility, and biocompatibility. However, the narrow-bandgap intrinsic characteristics required for NIR response inevitably lead to carrier concentration surge that exponentially increases dark current, while hot carriers undergo phonon scattering relaxation that suppresses carrier collection. In this work, the inherent limitations of narrow-bandgap polymer materials are overcome through a contactless direct current external electric field (EEF). The PTB7-Th:COTIC-4F device achieves an outstanding detectivity of 2.45 × 10¹³ Jones at 1100 nm, ranking among the highest values reported in the NIR spectral range. The applied EEF modulates both orientation and magnitude of electric dipole moments in acceptors, inducing ordered face-to-face molecular stacking, enhancing π-π interactions, and promoting J-aggregation, thereby facilitating fibrous network formation. Consequently, the optimized film morphology effectively suppresses energetic disorder and electron-phonon coupling, while simultaneously inhibiting exciton recombination and promoting exciton dissociation to achieve high-efficiency carrier transport. This non-contact external field modulation strategy establishes a novel pathway for developing high-performance NIR-OPDs.