Hybrid ionic-electronic semiconductors for interface engineering of ultra-low-dark-current solution-processed SWIR photodetectors

Shortwave infrared (SWIR) photodetectors are essential for industrial, medical, and security applications, but their adoption is limited by reliance on costly epitaxial semiconductors. Solution-processed organic and colloidal quantum dots (CQDs) semiconductors offer a promising alternative, although their devices often suffer from high dark current under reverse bias. We demonstrate an approach to precise work function modulation in SWIR photodetectors using conjugated polyelectrolytes with mixed counter-ions. This strategy achieves continuous work function tuning and interfacial defect passivation, significantly reducing dark current in solution-processed photodetectors. The optimized CQDs photodetectors exhibit a dark current density two orders of magnitude lower than conventional devices at −0.1 V bias (6.7 × 10−8 A cm−2), achieving a linear dynamic range of 130 dB, specific detectivity of 4.3×1012 Jones, and cutoff frequency of 107 kHz under 1550 nm illumination. Integrated with a CMOS read-out integrated circuit, the resulting SWIR imager demonstrates high-resolution performance (1280 × 1024 pixels), providing a viable alternative to InGaAs-based imagers.