Methyl-Terminated Germanene for a Robust Self-Powered Photoelectrochemical Photodetector

Functionalized germanene, a newly emerging 2D germanium semiconductor, has been widely investigated due to its unique electronic properties such as intrinsic bandgap and high carrier mobility. Herein, a photoelectrochemical (PEC) type photodetector based on methyl-terminated germanene (GeCH3) nanosheets with controllable thickness is realized by a solution-based exfoliation-centrifugation method. Impressively, the PEC-type photodetector based on GeCH3 nanosheets exhibits a high photocurrent density of 5.10 μA/cm2, photoresponsivity of ∼20 μA/W, and stable cycling under simulated sunlight irradiation. Such a photodetector shows self-powered behavior. The PEC photodetector also demonstrates a broad-spectrum photodetection capability, covering wavelengths from the UV to the IR region. Interestingly, the performance of such a photodetector can be tuned by varying the sample thickness through a solution-based exfoliation-centrifugation method. Combined with density functional theory simulations, the high performance of the PEC photodetector is attributed to the synergistic effect of effective visible light trapping, fast electron–hole separation, and improved interfacial charge transfer. The facile fabrication and high photoresponse indicate that the PEC photodetector based on ultrathin GeCH3 can provide a promising platform to study the PEC photodetector based on 2D materials. This work provides a promising platform for the investigation and application of photoelectronic devices based on germanene.