Radiation-Tolerant PbS CQD Thin-Film Photodiode-Based SWIR Image Sensors

Abstract

Short-wavelength infrared (SWIR) image sensors are of increasing interest for space applications, where ionizing radiation can significantly impact device performance. PbS colloidal quantum dot (CQD)-based thin-film photodiodes (TFPDs) are promising candidates due to their spectral tunability and compatibility with CMOS integration. However, their radiation response remains insufficiently understood. We investigated the effects of X-ray irradiation on PbS CQD-based SWIR TFPDs and image sensors up to a total ionizing dose of 220 krad. The results suggest that X-ray irradiation induces ligand-dependent modulation of the trap-state in PbS CQD films, leading to reduced recombination and enhanced carrier lifetime. Consequently, the TFPDs exhibit decreased dark current and improved external quantum efficiency (EQE), reaching 44.2% at 1420 nm. PbS CQD-based SWIR image sensors maintain stable operation after irradiation until 220 krad, achieving an EQE of 33.1%. These results provide an initial assessment of PbS CQD-based SWIR image sensors under X-ray total ionizing dose (TID) exposure, highlighting the importance of ligand-dependent CQD surface chemistry towards SWIR photodetectors in space applications.