Microscale PN Junctions by In Situ Sb Doping for High-Performance PbS Infrared Photodetectors

Room-temperature uncooled infrared photodetectors based on lead sulfide (PbS) offer significant potential for applications in the military, environmental, and automotive fields. While chemical bath deposition (CBD) offers cost and scalability advantages, inevitable oxygen doping and mandatory high-temperature sensitization impose fundamental limitations on device performance and integration. To address these challenges, this study reports an in situ antimony (Sb) doping strategy that enables the one-step growth of high-quality PbS films at room temperature. The introduced Sb dopant acts as a "sacrificial anode" to passivate the surface and suppress oxygen incorporation, which refers to the metallic Sb preferentially reacting with dissolved oxygen species, thereby "sacrificing" itself to protect the Pb²⁺ and S²⁻ ions from oxidation and preventing oxygen inclusion in the PbS lattice, thereby drastically reducing dark current. Meanwhile, it generates n-type PbS domains, spontaneously forming built-in microscale PN junctions with the p-type matrix to facilitate efficient charge separation. Consequently, the optimized Sb-doped PbS photodetector exhibits a superior performance with a low dark current of 0.21 mA at 1 V, a fast average response time of 39.25 μs, and a high specific detectivity of 5.36 × 10¹⁰ Jones at 2.6 μm, which is comparable to mainstream commercial uncooled devices. This in situ doping approach not only delivers a superior PbS photodetector but also pioneers a general pathway for engineering complex optoelectronic structures in solution-processed semiconductors.