Depleted Nanocrystal-Oxide Heterojunctions for High-Sensitivity Infrared Detection

: The goal of this project is to explore a new IR photodetector architecture based on a depleted ZnO/PbS QD heterojunction. Colloidal PbSQDs with the first excitonic absorption peak from 850-1050 nm were synthesized, and ZnO thin films were prepared by two different methods: thermal evaporation and solution processing. Devices with an optimized ZnO/PhS QD structure showed ultralow dark current, fast response, and a photocurrent on/off ratio greater than 10000. A comparative study of ZnO or PhS QD single-layer structures proved that the optical response arises from charge separation at a depleted junction forming between ZnO and PbS QDs. However, poor charge transport through the solution-processed ZnO and QD layers limits the photoconductive gain and quantum efficiency of devices.