Trap-Assisted Tunneling in PbS Colloidal Quantum Dots Photodetector

Currently, colloidal quantum dots (CQDs) photodetectors have shown significant advancement in the field of infrared photodetection. However, the immature analysis of dark current components hinders the realization of higher performance quantum dots optoelectrical devices. In this study, based on a PbS CQD photodetector, we employ a conventional dark current model of infrared photodetectors to analyze the dark current components of the device, yielding fitting results highly consistent with experimental observations. Our findings indicate that with increasing reverse bias, the dominant dark current components of the PbS CQD photodetector shift from diffusion (Diff) current, generation-recombination (G-R) current, and shunt (sh) current to trap-assisted tunneling (TAT) current. The band diagrams, recombination rates, carrier density distributions, and electric field intensity maps under different biases are further simulated, of which the theoretical results confirm that current components transition is attributed to the abundance of defects in quantum dot materials, leading to tunneling at the interface between the SnO2 layer and PbS-I layer under high bias conditions. Our work contributes to providing insight and direction for optimizing the CQD photodetector performances.