context: Owing to their attractive high carrier mobility, ambient stability, superior mechanical flexibility, large band gap and excellent optical properties, group IV–V compounds, as a new kind of 2D materials, show a promising potential application for optoelectronic devices. Herein, 2D GeP nanosheets were exfoliated by a facile LPE method and a photoelectrochemical (PEC)-type photodetector employing a doctor blade deposited 2D GeP nanosheet electrode on an ITO-coated glass was fabricated. Ultrafast carrier dynamics was carefully probed by transient absorption spectroscopy, and the parameters of the photodetector, such as the voltage and electrolyte concentration, were highly optimized. It shows remarkable performance with a responsivity of 187.5 μA W−1, a detectivity of 2.14 × 1012 Jones and an EQE of 61.3% at an ultraviolet wavelength of 380 nm. The proposed strategy avoids complicated material preparation and device fabrication and facilitates large-area photodetection.