High-performance solution-processed TIIG-based polymer photodetector with detectivity across scalable SWIR...

Developing cost-efficient, flexible, and Restriction of Hazardous Substances (RoHS)-compliant short-wave infrared (SWIR) photodetectors compatible with roll-to-roll processing remains a significant challenge. Here we present a simplified organic 'metal-semiconductor-metal' (MSM) photodetector featuring a single solution-processed bulk heterojunction of a newly synthesized thienoisoindigo-based ultralow-bandgap polymer, TIIG-Se-DFT, blended with the nonfullerene acceptor (NFA) Y6. The TIIG-Se-DFT polymer, incorporating selenophene and fluorinated thiophene units, combines a narrow bandgap of 0.96 eV with strong absorption across 700-1600 nm and forms films with local molecular order, enabling broadband light harvesting without multistep layer stacking. Device simplicity is achieved using an interdigitated Au electrode and a single solution-processed active layer, minimizing vacuum deposition and eliminating interlayer damage due to solvent exposure. The resulting photodetector reaches a specific detectivity (D*) of ≈2 × 10¹¹ Jones at 1150 nm, retains >0.13 × 10¹⁰ Jones at the eye-safe 1550 nm telecom band, and delivers 86/36 µs rise/fall times at 1 V_bias. Dark current is held to 4.6 × 10^-8 A cm^-2, and encapsulated devices preserve >95% responsivity after 800 hours of ambient aging. The simplified, high-sensitivity processing advances TIIG-Se-DFT:Y6 SWIR photodetectors toward industrial scale suitable for wearables, light detection and ranging (LiDAR), and optical communications.