High-Sensitivity SWIR Photodetector Based on PbS Quantum Dots via Solution-Phase MAPI Ligand Exchange

The use of LIDAR sensors is rapidly increasing across various fields, including autonomous transportation, robotics, security systems, and biosensing. Among the core components of LIDAR systems, short-wave infrared (SWIR) sensors play a crucial role in detecting infrared light reflected from objects to recognize the surrounding environment and humans. Various types of SWIR sensors have been reported, with growing demand for those capable of detecting eye-safe infrared wavelengths above 1400 nm. In particular, quantum dot (QD)-based SWIR sensors are attracting attention due to their tunable wavelength range within the eye-safe region, narrow full width at half maximum (FWHM), and selective detection with minimal interference from other infrared wavelengths. Moreover, QD-based SWIR photodetectors can be synthesized and fabricated via solution-based methods, offering advantages such as low cost and ease of fabrication. However, the long organic ligands typically present on QDs exhibit insulating properties, limiting the sensitivity and stability of the photodetectors. To address this issue, organic ligands can be replaced with short inorganic ligands possessing superior electrical conductivity. In this study, the organic ligands of synthesized PbS QDs were replaced with the inorganic ligand methylammonium lead iodide (MAPI) in solution, and a SWIR photodetector was fabricated. The MAPI-capped PbS QD-based photodetector exhibited remarkable external quantum efficiency (EQE) of 62%, a responsivity of 0.73 A/W, and a detectivity of 2.26 × 10¹¹ Jones within the 1400-1500 nm wavelength range.