SWIR Photodetectors and Upconversion Imaging With SN6‐TQ Conjugated Polymers

ABSTRACT The limited responsivity of broadband organic photodetectors (OPDs) in the short‐wavelength infrared (SWIR) region remains a critical challenge. Here, we report a novel conjugated polymer, PSN6TQ, by integrating the electron‐rich S, N‐heterohexacene (SN6) donor unit into a (1,2,5) thiadiazolo(3,4‐g) quinoxaline (TQ) backbone. This design synergistically enhanced the absorption coefficient (1.28 × 10 4 cm −1 ), elevated the lowest unoccupied molecular orbital (LUMO) energy level (‐3.60 eV), and improved hole mobility (1.15 × 10 – 3 cm 2 V – 1 s – 1 ), addressing the trade‐off between bandgap narrowing and charge transport in low‐bandgap polymers. The PSN6TQ‐based OPD demonstrated µs‐scale response speeds (rise/fall times of 1.3/1.8 µs) and achieved a 15.5% external quantum efficiency (EQE) at 1070 nm under zero bias, sustaining >10% EQE across the 925–1300 nm spectral range and >1% efficiency extending to 1455 nm. At the bias of ‐0.1 V, the device exhibited a specific detectivity ( D* ) of exceeding 10 10 Jones across 300–1500 nm and a linear dynamic range of 110 dB. Further engineering yielded a photomultiplication‐type OPD (MOPD) with > 100% EQE at 1.0 V and an organic upconversion detector (OUD) capable of real‐time SWIR imaging (at 1310 nm) with rapid response speeds (rise/fall times of 4.27/16.23 µs).