An ultraviolet-visible distinguishable broadband photodetector based on the positive and negative photoconductance effects of a graphene/ZnO quantum dot heterostructure

Broadband photodetectors covering the ultraviolet (UV) to visible range are significant for applications in communication and imaging. Broadband photodetectors with the capacity to distinguish wavelength bands are highly desirable because they can provide additional spectral information. Herein, we report a UV-visible distinguishable broadband photodetector based on a graphene/ZnO quantum dot heterostructure. The photodetector exhibits negative photoconductance under visible illumination because the adsorbents on graphene act as scattering centers to reduce the carrier mobility. In contrast, under UV illumination, the photodetector shows positive photoconductance as the photogenerated electrons in the ZnO quantum dots transfer to the graphene, thereby increasing the conductivity. Thus, the detection and distinction of UV and visible illumination can be realized by utilizing the opposing photoconductivity changes. These results offer inspiration for the design of multifunctional broadband photodetectors