High responsivity colloidal quantum dots phototransistors for low-dose near-infrared photodetection and image communication

The surging demand and adoption of infrared photodetectors (IRPDs) in sectors of imaging, mobile, healthcare, automobiles, and optical communication are hindered by the prohibitive costs of traditional IRPD materials such as InGaAs and HgCdTe. Quantum dots (QDs), especially lead chalcogenide (PbS) QDs, represent the next-generation low-bandgap semiconductors for near-infrared (NIR) detection due to their high optical absorption coefficient, tunable bandgap, low fabrication costs, and device compatibility. Innovative techniques such as ligand exchange processes have been proposed to boost the performance of PbS QDs photodetectors, mostly using short ligands like 1,2-ethanedithiol (EDT) and tetrabutylammonium iodide (TBAI). Our study explores the use of long-chain dithiol ligands to enhance the responsivity of PbS QDs/InGaZnO phototransistors. Long-chain dithiol ligands are found to suppress horizontal electron transport/leakage and electron trapping, which is beneficial for responsivity. Utilizing a novel ligand-exchange technique with 1,10-decanedithiol (DDT), we develop high-performance hybrid phototransistors with detectivity exceeding 10¹⁴ Jones. Based on these phototransistors, we demonstrate image communication through a NIR optical communication system. The long-ligand PbS QDs/InGaZnO hybrid phototransistor demonstrates significant potential for NIR low-dose imaging and optical communication, particularly in scenarios requiring the detection of weak light signals at low frequencies.