Abstract
Transition metal dichalcogenides (TMDCs) have not only recently attracted tremendous attention due to their unique optical and electrical properties but also the interesting and various nanostructures created by different synthesis process. These atomically thin TMDCs materials possess great potential in sensing, optoelectronic, energy harvesting and Li-ion battery applications. However, the atomic thickness of TMDCs will limit the light absorption and result in weak performance of optoelectronic devices, such as photodetectors. Here, we demonstrate a novel approach to increase the surface area of TMDCs in the one-step synthesis process of TMDC nanowalls from WOx into WS2 nanowalls. By utilizing the rapid heating and rapid cooling process, we can achieve the formation of nanowalls with the height of ~150 nm standing perpendicularly on top of the substrate. Our method provides a rapid synthesis process with enhanced aspect ratio compared to the conventional solid-vapor phase CVD process, which is commonly used for the synthesis of planar TMDCs with few atomic layers. Moreover, the combination of colloidal quantum dots (QDs) with three different emission wavelength and WS2 nanowalls will further improve the performance of WS2-based photodetector devices, including 3.5~4 times photocurrent enhancement and shorter response time. The remarkable results of the QD-WS2 hybrid devices to the high NRET efficiency between QDs and our nanostructured material are caused by the spectral overlap between the emission of QDs and the absorption of WS2. Additionally, the outstanding NO2 gas-sensing properties of QDs/WS2devices were demonstrated with a remarkably low detection limit down to 50 ppb with a fast response time of 26.8 s contributed by tremendous local p-n junctions generated from p-type WS2 nanowalls and n-type CdSe-ZnS QDs. Our work successfully reveals the energy transfer phenomenon in QD-WS2 hybrid devices and shows great potential in commercial multifunctional sensing applications.