The fact that in all photocathodes (Sb2Se3, Si, Cu2O) the Rrec1 and Rrec2 increase with increasing negative potential, indicating higher resistances at higher photocurrent region, further supports that both resistances are related to a recombination process that is suppressed upon more negative applied voltages. Compared with the Cu2O and Sb2Se3 photocathodes, the Rrec2 in the Si photocathode rapidly increases, as the applied potential becomes increasingly negative (Figure ), meaning that at a sufficiently negative potential the photo-generated electron-hole pairs in the Si photocathode are less likely to recombine. The steeper increase of Rrec2 in the Si photocathode is in accordance with the relatively better fill factor of the Si photocathode (Figure in the Supporting Information). Additionally, the Cdep of all materials have a similar potential dependence corresponding to a p-type semiconductor (Figure ). The Mott-Schottky plots obtained by the Cdep values of the Si and Cu2O photocathodes yield doping densities of 2.39×10 15 and 3.78×10 14 cm -3 , respectively (Figure in the Supporting Information). These values are also in good agreement with the specification value of the commercial Si wafer (boron doped, 10 to 30 Ohm cm) and the value for thermally oxidized Cu2O in the literature, further verifying our interpretation and assignment of the depletion capacitance of the photoabsorber. Based on the resistance and capacitance values, we can calculate the characteristic time constants for the associated processes by multiplying the two values (=R×C, Figure ). As we observed two different semi-circles, two different time constants (1=Rrec1×Cdep and 2=Rrec2×Cinter) can be obtained from all photocathodes. However, since the 2 is always much higher than 1 by more than 3 orders of magnitude (Figure in the supporting information), the overall lifetime is determined by the 2 (1+22). The overall time constant represents the effective time until the photo-generated carriers recombine, i.e. the minority carrier lifetime. In the photocurrent region, the lifetime of the photo-generated carriers (Figure ) is much longer than the time constants for charge transfer (see also Figure in the supporting information), so that the carriers can be transferred to the electrolyte to drive the HER. On the other hand, before the photocurrent onset, the recombination process is much faster than the charge transfer reaction, causing the charges to recombine. In all photocathodes, the lifetime increases as the applied potential increases after photocurrent onset, indicating the photo-generated carriers can survive a longer time until they recombine under large band bending conditions. The saturated lifetimes are approximately 0.5 s, 0.1 s, and 0.5 μs for Si, Sb2Se3, and Cu2O photocathodes, respectively. It is generally accepted that metal oxide semiconductors have shorter lifetimes than chalcogenide and/or crystalline Si due to the strong ionic nature of metal oxides. The shorter lifetimes in the Cu2O photocathode, meaning that a relatively large number of carriers in the Cu2O photocathode would recombine, could be one origin of the relatively low photocurrent of the Cu2O photocathode (Figure in the supporting information), although the appearance of an additional R-C element probably related to the Ga2O3 has still to be fully understood as it could contribute to the slowing down of the actual recombination process. as it is likely that more recombination takes place due to the increased population of the photogenerated charges under the higher light intensity. The Cdep of both Sb2Se3 and Cu2O photocathodes has a higher value under the higher light intensity (Figure ). The Mott-Schottky plots obtained by the Cdep under 50% sun light yield 5.97×10 18 and 1.01×10 15 cm -3 for Sb2Se3 and Cu2O photocathodes, respectively, which are slightly higher values than for the 10% sun case (2×10 17 cm -3 and 3.78×10 14 cm -3 ) due to the photo-generated carrier contribution (Figure ). These higher capacitance values of Cdep at a higher light intensity were also reported in an impedance study on Si solar cells. This observation in our system further substantiates the assignment of Cdep in our model to the depletion regions in the light absorber material. Additionally, the overall lifetimes of the minority carriers (τ2) at 50 % sun are smaller than at 10 % sun in both photocathodes (Figure ). This means the recombination process takes place at a faster rate under a higher light intensity due to the increased population of photogenerated minority carriers. The light intensity dependence, showing the expected differences in the resistances, capacitances, and lifetimes of both Sb2Se3 and Cu2O light absorbing semiconductors, further verifies that our equivalent circuit model reflects the observed photophysical and electrochemical processes and properties and can be used as a useful diagnostic tool for multi-layered photocathodes.