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.