All-optical 2D perovskite photodetector arrays for pixelated long-wave infrared imaging

Infrared detection and imaging are important for applications including thermal monitoring, night vision, environmental sensing, and molecular identification. All-optical mid-wave infrared (MWIR) and long-wave infrared (LWIR) detection offers a compelling alternative to conventional infrared detectors by enabling non-contact photothermal sensing without needing electronic readout circuitry. Here, we demonstrate pixelated LWIR imaging using solution-processed two-dimensional metal-halide perovskites (2D-MHPs), whose strong electron-phonon interaction produces a large temperature coefficient of reflectance in the visible wavelength range. By integrating (PEA)₂PbI₄ films with LWIR-absorbing SiNₓ membranes, we realize centimeter-scale imagers capable of detecting 9.5-µm LWIR light with sensitivity down to ~20 pW·µm⁻². To mitigate lateral thermal diffusion that limits spatial fidelity, we introduce a structured-probe illumination scheme, and we further develop a fully pixelated imager with thermally isolated membrane-disc arrays. This design effectively eliminates pixel-to-pixel crosstalk and enables high-resolution optical readout using a silicon-based CMOS camera. These advances establish 2D-MHP-based all-optical thermal imaging as a scalable, low-cost platform for LWIR sensing, with strong potential for extension to far-infrared and terahertz detection.