In situ iodine-doped sensitization for enhanced mid-infrared detection in PbSe thin films

Abstract

Conventional sensitization methods for lead selenide (PbSe) films typically involve annealing in an atmosphere containing iodine, oxygen, and nitrogen, where iodine plays a pivotal role. However, these approaches face limitations in achieving uniform and precise iodine incorporation. In this study, we propose an in situ iodine-doped sensitization process based on chemical bath deposition, offering a streamlined alternative. This one-step synthesis of iodine-doped PbSe films enables efficient sensitization, allowing for comprehensive control over dopant concentration. Systematic investigations reveal that iodine doping reduces the bandgap (from 0.317 eV to 0.303 eV), suppresses electron–hole recombination, and extends carrier lifetimes. At an optimal potassium iodide (KI) concentration of 1.8 × 10^–3 mol/L, the sensitized PbSe films exhibit a detectivity of 1.81 × 10⁹ Jones and a rapid response time of 1.97 ms under 1550 nm infrared illumination. Combined with X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectroscopy (EDS) analyses, we demonstrate that iodine migration promotes lattice oxygen incorporation at grain boundaries, forming sensitization centers critical for enhanced photoconductivity. This work not only simplifies the sensitization process but also provides mechanistic insights into PbSe-based infrared photodetectors, highlighting its potential for scalable and cost-effective fabrication.