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

Area of Science:

• Materials Science
• Optoelectronics
• Quantum Dot Technology

Background:

• Short-wavelength infrared (SWIR) image sensors are crucial for space applications.
• Ionizing radiation poses a significant threat to the performance of these sensors.
• Lead sulfide colloidal quantum dot (PbS CQD)-based thin-film photodiodes (TFPDs) offer tunable spectral response and CMOS compatibility, making them promising for SWIR imaging.

Purpose of the Study:

• To investigate the effects of X-ray irradiation on PbS CQD-based SWIR TFPDs and image sensors.
• To understand the radiation response mechanisms in PbS CQD films.
• To assess the suitability of these devices for space applications under ionizing radiation.

Main Methods:

• Exposure of PbS CQD-based SWIR TFPDs and image sensors to X-ray irradiation up to a total ionizing dose (TID) of 220 krad.
• Analysis of device performance metrics including dark current and external quantum efficiency (EQE).
• Investigation of ligand-dependent modulation of trap states in PbS CQD films.

Main Results:

• X-ray irradiation induced ligand-dependent modulation of trap states in PbS CQD films, reducing recombination and enhancing carrier lifetime.
• PbS CQD TFPDs showed decreased dark current and improved EQE, reaching 44.2% at 1420 nm.
• PbS CQD-based SWIR image sensors maintained stable operation up to 220 krad, with an EQE of 33.1%.

Conclusions:

• PbS CQD-based SWIR image sensors demonstrate resilience to X-ray irradiation up to 220 krad.
• Ligand-dependent surface chemistry is critical for optimizing SWIR photodetectors in radiation-intensive space environments.
• These findings support the potential of PbS CQD technology for robust space-based SWIR imaging.