High-Sensitivity Photodetectors Based on Silver Nanowires/Silicon Nanopillar Arrays

Light loss is one of the main factors affecting the quantum efficiency of photodetectors. Several approaches have been proposed to mitigate light loss and improve the quantum efficiency of silicon-based photodetectors. Here, we demonstrate high-sensitivity photodetectors based on highly antireflective silicon nanopillar arrays (Si-NPAs) as a light trapping layer combined with a thin film of silver nanowires (Ag-NWs) in a mesh configuration. This composite structure overcomes the weak light absorption and severe surface complexation of conventional silicon-based photodetectors. Introduction of Ag-NWs provides multiple transmission paths for electron transfer without affecting the photodetector light absorption, while the formation of Schottky junctions with Si-NPAs promotes photoelectric conversion. In addition, the effects of different concentrations of Ag-NWs films on the performance of Si-NPAs photodetectors are investigated. The proposed photodetector exhibits the best performance when the concentration of Ag-NWs is 6 mg/mL. At this optimized concentration of Ag-NWs, the external quantum efficiency (EQE) is 82.4% at 850 nm, which is $5.8\times $ higher than that of a single Si-NPAs photodetector. Furthermore, the network structure of Ag-NWs promotes the fast response of the device with a short rise/fall time of 80/ $72 \mu \text{s}$ , which is about half of the response time of a single Si-NPAs photodetector. The combination of Ag-NWs and silicon nanopillars has the potential to open up new possibilities for the development of highly sensitive photodetectors.