Dual ligands-assisted oxidation strategy for suppressing dark current in PbS quantum dot infrared photodetectors

Lead sulfide colloidal quantum dots (PbS CQDs) are potential optoelectronic semiconductor materials for short-wave infrared (SWIR) photodetectors owing to their tunable bandgap, high absorption coefficient, and monolithic integrability with silicon readout circuits. However, incomplete surface passivation of {100} facets in large-size PbS CQDs (diameter > 4 nm) and ubiquitous halide ions migration in CQDs films have resulted in high dark current in PbS CQDs SWIR photodetectors. Herein, a dual ligands passivation combined with in-situ oxidation strategy is proposed to improve the surface passivation of CQDs and suppress the ions migration process. The advanced dual ligands could effectively passivate the polar {111} and non-polar {100} facets to reduce trap states in CQDs films, while the subsequently controllable thermal process could restrict the ions migration by interrupting the transport pathway to improve stability. The resultant PbS CQD infrared photodetectors exhibit remarkably reduced dark current and maintain almost unchanged photoresponse. The optimized photodetector exhibits a responsivity of 22.88 mA/W and a specific detectivity of 1.14 × 10 11 Jones at 1300 nm under a 1 V bias, demonstrating an alternative approach toward high-performance SWIR photoelectronic devices.