Uncooled Mid-Wavelength Infrared Photoconductive Detectors Based on PbSe Nanocrystals

Low-cost, uncooled photodetectors operating in the spectral regions of mid-wavelength infrared (MWIR = 3-5 μm) and long-wavelength infrared (LWIR = 9-12 μm) are anticipated to dominate the future infrared market with its impacts broadly ranging from night driving assist, to drone and microsatellite mounts, to machine vision and augmented goggles. Research interest in lead selenide (PbSe), an 80-year-old technology, has reemerged in recent years, due to its advantageous low manufacturing cost and Auger-suppression properties, as a potential candidate to bridge the current MWIR technology gap. While chemical bath deposition (CBD) and vapor phase deposition (VPD) have been the two major established techniques to fabricate PbSe photoconductive films, they can benefit by adopting the emerging solution-processed fabrication methods to improve the detector manufacturability. In this study, we report on the MWIR photoconductive film derived from colloidal PbSe nanocrystals and demonstrate detectors that reach a specific detectivity of 8 × 10⁸ Jones (200 Hz, 2 V bias) at room temperature. While the sensitization process bears a similarity to the conventional CBD- or VPD-grown PbSe films, the colloidal nanocrystal nature of the starting material requires different processing conditions to reach high responsivity, and those are highlighted in this work. In light of the emergent need for low-cost, uncooled MWIR photodetector technology, the results presented here may serve as a first stepping stone toward future digital additive manufacturing of infrared sensors and imagers.