Nano-to-Microporous Networks via Inkjet Printing of ZnO Nanoparticles/Graphene Hybrid for Ultraviolet Photodetectors

摘要： Inkjet-printed photodetectors have gained enormous attention over the last decade. However, device performance is limited without post-processing, such as annealing and UV exposure. In addition, it is difficult to manipulate the surface morphology of the printed film using an inkjet printer due to the limited options of low viscosity ink solutions. Here, we employ a concept involving the control of the inkjet-printed film morphology via modulation of co-solvent vapor pressure and surface tension for the creation of a high-performance ZnO-based photodetector on a flexible substrate. The solvent boiling point across different co-solvent systems is found to affect the film morphology, which results in not only distinct photo-response time but also photo-detectivity. ZnO-based photodetectors were printed using different solvents which display a fast photo-response in low-boiling point solvents due to the low carbon residue and larger photo-detectivity in high-boiling point solvent systems due to the porous structure. The porous structure is obtained using both gas-liquid surface tension differences and solid-liquid surface differences, and the size of porosity is modulated from nano-size to micro-size depending on the ratio between two solvents or two nanomaterials. Moreover, the conductive nature of graphene enhances the transport behavior of the photocarrier, which enables a high-performance photodetector with high photo-responsivity (7.5*102 AW-1) and fast photo-response (0.18 s) to be achieved without the use of high-boiling point solvents.