HgSe/PbS Core-Shell Colloidal Quantum Dots Synthesized by a Simple Two-Step Method for Room-Temperature Long-Wave Infrared Photodetection

Mercury chalcogenides (HgX) colloidal quantum dots (CQDs), particularly mercury selenide (HgSe) CQDs, have emerged as a promising candidate for long-wave infrared (LWIR, 8–14 μm) photodetectors due to their exceptional bandgap tunability by solution processing. Nevertheless, the intrinsic limitations of bare HgSe CQDs—high surface defect density and oxidation susceptibility—severely compromise their optoelectronic performance. In this paper, a simple two-step method to grow high-quality HgSe/PbS core-shell CQDs in the LWIR region by synergistically optimizing the thickness of the PbS shell for surface passivation and the oxidation resistance of the HgSe cores is presented. Further, its applications in LWIR detection are explored using a simple metal–semiconductor–metal (MSM) based photodetector Au/(HgSe/PbS)/Au. As a result, a high responsivity of 42 mA/W with a high specific detectivity of 2.41 × 109 Jones under a 25 mW/cm2, 10 μm illumination is obtained from the LWIR photodetector Au/[HgSe(13 nm)/PbS(5 nm)](1 μm)/Au at room-temperature. Therefore, such a simple two-step method of core-shell engineering approach establishes a versatile platform for developing next-generation LWIR optoelectronics.