Electrode Engineering of Colloidal Quantum Dot Photodetectors Using a Self-Assembled Island-like LiF Interfacial Layer

Lead sulfide (PbS) colloidal quantum dot (CQD) photodetectors (PDs) are promising devices for low-cost, high-performance, and large-area infrared imaging. To achieve commercial applications, it is necessary not only to further improve performance but also to achieve high stability. In this study, the uncontrolled migration of the Au element into the PbS CQD layers was identified. An interface passivation approach was employed, which involved the implementation of a self-assembled island-like LiF interfacial layer between the PbS-EDT layer and the Au electrode. The approach effectively mitigated the detrimental migration of the Au element and substantively enhanced the stability of PbS CQD PDs. At the same time, this strategy substantially suppressed the dark current in the PbS CQD PDs due to interface passivation, which led to more than 2-fold improvements of the specific detectivity to 4.8 × 1012 Jones. A PbS CQD photodiode imager based on the thin-film transistor readout circuit was finally fabricated. Penetration imaging and material discrimination imaging were demonstrated successfully by the PbS CQD imager.