Suppressing the Dark Current of PbS QD SWIR Photodetector by Freeze-Treated Hole Transport Layer

Abstract

Lead sulfide (PbS) quantum dot (QD) photodetector is considered as a key component of the next-generation infrared machine vision applications for its wide detection range and effective fabrication cost. Leakage current caused by film cracks and trap states during the film fabrication stops the further optimization of device performance and slows down the industrialization of the PbS QD photodetector. An optimized hole transport layer based on PbS QD with minimized cracks and trap states is achieved through a freeze-centrifugation purification before the ligand-exchange process, leading to a suppressed dark current density (260 nA/cm $^{{2}}\text {)}$ , strongly reduced noise current (26 fA/Hz $^{{1}{/{2}}}\text {)}$ . Enhanced film quality brings an ultra-high detectivity ( ${5}.{47}\times {10} ^{{12}}$ Jones) and faster response-time ( $1.4\mu$ s) of the freeze-treated photodetector under zero bias.