Enhancing the sensitivity of flexible acoustic wave ultraviolet photodetector with graphene-quantum-dots decorated ZnO nanowires

Graphene quantum dots decorated zinc oxide nanowires (GQDs@ZnO-NWs) were applied to enhance sensing performance of highly flexible and transparent surface acoustic wave (SAW) ultraviolet (UV) photodetectors made on ultra-thin flexible glass. The developed flexible SAW sensors possess better performance than that of the previously developed polymer based flexible SAW devices, due to insignificant acoustic loss of flexible glass substrate. UV sensitivity of the flexible glass based SAW sensors was enhanced by three times, and the response time was shorten by four times after the sensor was coated with the GQDs@ZnO-NWs hybrid nanomaterials. These improvements are mainly attributed to: (1) large specific surface areas of ZnO NWs which can generate a large number of photon-generated carriers; (2) introduction of GQDs which can reduce the carrier recombination rate. The resonant frequency of flexible glass SAW UV photodetectors exhibited a good repeatability and stability in responses to cyclic changes of the UV lights at different wavelengths. They also maintained a good performance under a bending angle of ∼30° for 200 times without apparent degradation, showing the excellent flexibility and stability of the UV photodetector.