Efficient near-infrared lead sulfide quantum dots photodetectors fabricated using an excess PbBr2 passivation process

Abstract

Recently, lead sulfide colloidal quantum dots (PbS CQDs) have demonstrated great potential in becoming one of the promising material candidates for next-generation photodetectors. PbS CQDs provide outstanding properties including size dependent bandgap tunability, high absorption coefficient, solution processability, and multiple exciton generation effects. However, a crucial criterion for the fabrication of high-performance photodetectors is the effective surface passivation of quantum dots,which can facilitate carrier transport. Conventional solution-phase ligand exchange cannot effectively passivate the <100> facets of quantum dots, leading to an increase in deep defects and a degradation of device performance. Herein, an efficient near-infrared PbS CQDs photodetectors fabricated by using an excess PbBr2 (lead bromide) passivation process is reported. By adjusting the proportion of PbBr2 in the solution phase transition, the quality of quantum dot films have been improved. Meanwhile, the photocurrent of the detector is boosted while the dark current is suppressed. According to the research results, the photodetector exhibits excellent rectification characteristics (2.91×10²) and a high on/off ratio (1.8×10³).The external quantum efficiency (EQE) of the PbS CQDs photodetector at 980 nm reaches 30% and the responsivity can reach 0.247 A/W. In addition, the detectivity of the detector can reach 1.57×10¹⁰ Jones. These results which are obtained here should be of great values in designing advanced PbS CQDs-based near-infrared photodetectors for applications in future.