Size-controllable fabrication of PbS quantum dots for NIR–SWIR photodetectors with extended wavelengths†

A short-wave infrared (SWIR) photodetector requires robust performance and cost-effectiveness due to its utilization in military and civilian applications. Lead sulfide quantum dots (PbS QDs) have gained increasing attention in the field of near-infrared (NIR) detection owing to their heightened sensitivity and adjustable infrared absorption properties. Yet, it remains a great challenge to fabricate large-sized PbS QDs with the expansion of detection capabilities from NIR to SWIR regions. Here, a hot injection method was proposed to successfully synthesize large-sized PbS QDs with a diameter of 12.2 nm. The obtained PbS QDs in the 90s extended the detectable wavelengths to 2220 nm resulting from their large size. Subsequently, a photodetector device operating in the SWIR region was fabricated by employing PbS QDs as the photoactive layer. The specific detectivity of the device at ambient temperature reaches 4.0 × 10¹¹ Jones at 2100 nm, which shows promising applications.