Tin-Lead-Selenide Nanocrystals for Sensitive Uncooled Mid-Infrared Focal Plane Array Imager with Monolithic Readout Integration.

The mid-infrared focal plane array (FPA) imager has developed over recent decades to become multifunctional, powerful, reliable, miniaturized, and cost-effective. However, the complexity of the refrigerated packaging process (such as dewar flask) and traditional fabrication technology (such as flip-chip) continues to contribute significantly to the high cost of industrial production. Here, a simple, low-cost, and effective type of uncooled mid-infrared FPA imager is reported through the monolithic integration of mid-infrared Pb_1-xSn_xSe nanocrystals (NCs) PIN heterojunction (PbS/Pb_1-xSn_xSe/ZnO) photodetectors and glass-based readout integrated circuits (ROICs). Sn-doping in PbSe NCs not only weakens the internal photocarrier-phonon coupling to reduce thermal noise but also optimizes the energy band structure of the heterojunction to enhance mid-infrared performance. Finally, the PbS/Pb_0.86Sn_0.14Se/ZnO heterojunction photodetector demonstrates a dark current (2.7 x 10^-7 A mm^-2 at -0.5 V), a detectivity of 7.46 × 10⁹ Jones at a peak wavelength of 4.25 µm, air stability (retaining 96.7% performance at 300 K for 360 days) and the corresponding uncooled mid-infrared FPA (64 × 64 pixels) achieves excellent thermal sensitivity of 133 mK. These results underscore the substantial potential applications of mid-infrared FPA based on the heterojunction, including spectral imaging, gas leak detection, and chemical reagent identification.