Core-shell structure induced surface reconstruction of PbS quantum dots toward high-detectivity short-wave infrared photodetectors

Abstract

Surface passivation and reconstruction in quantum dot (QD) materials are crucial for enhancing the performance of optoelectronic devices, particularly in high-sensitivity, low-noise short-wave infrared (SWIR) photodetectors (PDs). This study presents an optimized approach for PbS/CdS core-shell QDs through optimized surface engineering through controlled CdS shell modulation and solution-phase ligand exchange with concentrated lead halides. The refined surface reconstruction significantly reduces QD aggregation and reduces trap states, resulting in ordered QD stackings with narrower energy distributions. Consequently, the QD PDs achieve a significantly reduced dark current density of 192 nA cm⁻² and an enhanced detectivity of 5.06 × 10¹² Jones, resulting in a 29.6% reduction in dark current and a 7.4-fold improvement in detectivity compared to pristine QD PDs. Electrochemical impedance spectroscopy confirms the reduction in trap-assisted recombination, supported by extended photoluminescence lifetimes and higher quantum efficiencies. These findings underscore the potential of surface reconstructed QDs for advanced SWIR PD applications, particularly in achieving high sensitivity in imaging systems.