Ligand-directed growth control for high-performance short-wave infrared quantum dot photodetectors

Abstract

Colloidal PbS quantum dots (QDs) are promising for short-wave infrared (SWIR) photodetection and imaging but intrinsically suffer from surface defects and poor stacking configuration in solids. Here, we employ 1-octanethiol (OT) mixing with bis(trimethylsilyl) sulfide (TMS) as double sulfur sources to dynamically regulate PbS QD growth and surface passivation. By optimizing the OT/TMS ratio, the resulting QDs exhibit improved monodispersity, reduced surface defects, and prolonged carrier lifetimes. Grazing-incidence small-angle X-ray scattering (GISAXS) reveals that OT drives QDs toward octahedral-like morphologies and orders body-centered cubic superlattices, distinct from the truncated octahedral and face-centered cubic structures of control QDs. Such morphology with less (100) facet regulation reduces the trap density and enhances inter-dot electronic coupling after ligand exchange. Devices based on the OT-QDs demonstrate suppressed dark current, higher external quantum efficiency (59.1% at 1308 nm), and improved specific detectivity reaching 8.34 × 10¹¹ Jones.