Low‐Noise Visible‐NIR Quantum‐Dot Photodetection and Imaging Enabled by Ligand Post‐Engineering

ABSTRACT

PbS quantum dots (QDs) are highly promising visible–near‐infrared materials for low‐noise broadband photodetectors, particularly in a state‐of‐the‐art homojunction device made solely from p‐ and n‐doped QDs. However, the performance of these QD photodetectors is frequently bottlenecked by the inferior quality of p‐doped PbS QDs. This limitation originates from the poor ligand control of p‐doped QDs during the constrained and incomplete solid‐phase synthesis, resulting in significant energy‐level disorder and aggravated carrier recombination in the device. Here, we propose an ethylenediamine (EDA) post‐treatment strategy to refine the ligand environment of p‐doped PbS QDs after synthesis. This EDA treatment efficiently removes the residual insulating oleate ligands by 91.4%, while promoting further bonding of the target thiol ligands. The mild chemical nature of EDA ensures that pre‐deposited functional layers remain entirely unaffected. Photodetectors incorporating EDA‐treated p‐doping QDs exhibit significantly suppressed noise (3.07 × 10 ⁻¹⁴ A Hz ^−1/2 ) and achieve an ultrawide bandwidth of 205 kHz for high‐speed operation. These high‐performance detectors enable rapid and clear broadband single‐pixel imaging through various opaque media, demonstrating their considerable potential for machine vision, autonomous sensing, and imaging under challenging environments.