Origin of the Low-Frequency 1/f Noise of a Photoelectrochemical Photodetector

The low-frequency photocurrent noise power density ${S}_{I}$ of a self-powered photoelectrochemical photodetector (PEC PD) based on InGaN/Cu2O core-shell nanowire p-n junctions follows a 1/ ${f}^{\beta }$ frequency dependence. The exponent $\beta $ increases from 1.5 to about 2 with increase of the photocurrent density ${I}_{p}$. ${S}_{I}$ strongly deviates from the standard quadratic ${I}_{p}$ dependence with an exponent of 1.6. The noise behavior of the dark current density driven by an external voltage is very similar. $\beta $ distinctly depends on the NaI electrolyte concentration. Hence, the physical origin of the low-frequency 1/ ${f}^{\beta }$ noise is the redox noise generated by the Faradaic charge transfer at the electrode-electrolyte interface. The redox noise dominates the total noise of the PEC PD.