context: To evaluate the performances of 2D GeP nanosheet-based photodetectors at an exact wavelength, selected wavelengths of lights (350, 365, 380, 400, 475, 550 and 650 nm) were employed (Fig. 4) in 0.1, 0.5 and 1 M KOH electrolytes. It is clear to see that the photocurrent density values are greatly smaller than the values under simulated light because of inferior light irradiation. The photocurrent density and photoresponsivity show a similar trend to the results in a simulated light state. Notably, it is also shown that such 2D GeP nanosheet-based photodetectors exhibit a higher sensitivity at a short wavelength range, especially at 350, 365 and 380 nm (Fig. 4c, f and i) and the highest photoresponsivity is 187.5 μA W−1 at 380 nm wavelength, 0.6 V applied bias potential and in 0.5 M KOH electrolyte. The above photo-response results at different wavelengths are in strong agreement with the UV-Vis absorption spectrum in Fig. 1g. Such results demonstrate great potential for high-performance UV-Vis photodetector application.
answer: 0.5 M KOH