Synergy between Fermi Level of Graphene and Morphology of Polymer Film Allows Broadband or Wavelength-Sensitive Photodetection

Deliberately tuning the photodetecting performances of polymer/graphene (G) hybrid films through a simple approach and understanding its underlying mechanisms are of significance for developing related devices. Herein, photodetecting features of polymer/G films are successfully tuned from broadband to IR/UV sensitive through a simple thermal treatment, providing optional working modes for varied demands. The morphologies and electronic/photodetecting properties of polymer/G hybrids are characterized in detail through atomic force microscopy, scanning electron microscopy, grazing-incident wide angle X-ray scattering, field effect transistor devices, and density functional theory calculations. The results suggest that the synergetic effect between Fermi level of G and morphologies of polymer film is responsible for the altered sensitivities to different radiations. The former factor shifts the energy barrier of charge carrier transferring for photocurrent generation, while the latter modifies the absorption capabilities of polymer films to the specific lights. Thus, in this work, besides proposing an in-principle multimode photodetecting device for different applications, the intrinsic mechanisms behind the performance modifications and the robust capabilities of simple thermal treatments on tuning activities of polymer/G devices are revealed as well, which provide valuable supports for developing efficient photosensing devices in a facile and rational approach.