Direct synthesis of p-type PbS quantum dot inks toward wafer-scale SWIR imaging

PbS quantum dots (QDs) are highly promising for scalable short-wave infrared (SWIR) optoelectronics due to their tunable bandgap and solution-processability. While efficient devices require well-defined p-n homojunctions, the fabrication of p-type QD layers remains a critical bottleneck compared with the well-established n-type QD inks. Current fabrication of p-type QD layers relies on solid-state ligand exchange (SSLE). However, SSLE suffers from incomplete ligand replacement and non-uniform oxidation, causing film inhomogeneity that prevents wafer-scale manufacturing. Here, we report a direct synthesis of p-type PbS QD inks with tunable QD size, optical absorption, and p-type electronic characteristics. The resulting inks yield conductive p-type films on 6-inch Si substrates with highly uniform thickness. Using this strategy, we realize SWIR photodetectors with fully ink-processed PbS QD p-n junctions, together with a prototype imaging module. When integrated with a recognition algorithm, the imager provides SWIR images that facilitate vehicle recognition under foggy conditions. This work establishes a scalable route toward future high-performance, wafer-level SWIR optoelectronic platforms.