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 dot (CQD) 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 counterions. This strategy achieves continuous work function tuning and interfacial defect passivation, significantly reducing dark current in solution-processed photodetectors. The optimized CQD photodetectors exhibit a dark-current density two orders of magnitude lower than that of 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 complementary metal-oxide-semiconductor read-out integrated circuit, the resulting SWIR imager demonstrates high-resolution performance (1280 × 1024 pixels), providing a viable alternative to InGaAs-based imagers.