Efficient interface and bulk passivation of PbS quantum dot infrared photodetectors by PbI2 incorporation

Abstract

Lead sulfide colloidal quantum dots (PbS CQDs) exhibit outstanding optoelectronic properties owing to their low temperature solution-processability and bandgap tunability. PbS QD heterojunction detectors suffer from an incomplete interface and bulk passivation. Herein, a simple passivation method based on PbI₂ was developed, which can effectively suppress the heterojunction interface and PbS QD surface defects by interface and ligand passivation. Utilizing the present strategies, PbS QD photodetectors can decrease the dark current and simultaneously increase the photocurrent. Such photodiode detectors also showed a fast response on the order of microseconds which is much faster than that of photoconductive CQD detectors (millisecond order). Also, an ultra-high specific detectivity of 10¹³ Jones was obtained. Meanwhile, the energy conversion efficiency of PbI₂ based devices reached 8%, a twofold value compared to the control one. The convenient and efficient passivation method is expected to hold great potential for high performance QD optoelectronic devices.