There is another possibility to fit our EIS data with a different EC model, the so-called Maxwell circuit, which might lead us to a slightly different interpretation (see Figure in the Supporting Information). With the Maxwell circuit model, Rrec solely represents the recombination process in the depletion region while Rinter is associated with the charge trapping resistance and/or a charge accumulation (Cinter) at the Sb2Se3/TiO2 interface. As both models give us valid values of Cdep and time constants (Figure -d, Supporting Information), it is difficult for now to conclude that one model is correct while the other is not. However, regardless of which of these two models is chosen, the clear message we obtain from the EIS data are that we can investigate the depletion region capacitance by Cdep and the two resistances are associated with a recombination process at the Sb2Se3/TiO2 interface. Therefore, the schematic showing the EC model mapped onto the band structure of Sb2Se3 photocathodes can be drawn as shown in Figure (or in terms of the Maxwell circuit see Fig. ). As shown thus far, we can investigate the properties of the Sb2Se3 light absorber layer under operando conditions by considering the two increasing semi-circles after the photocurrent onset in the Nyquist plots. To show the versatility of this R-C elements-based approach, we further analyzed Si and Cu2O photocathodes with similar device configurations as shown in Figure . Note that there is an additional layer of Ga2O3 in the Cu2O photocathode and the Cu2O photocathode revealed a much higher photocurrent onset (~0.8 VRHE) compared to the Si photocathode counterpart (~0.2 VRHE). As we already showed above and our previous study, the resistances associated with the TiO2/catalyst interface (RTiO2) and the catalyst/electrolyte interface (RCT) appear before the photocurrent onset and revealed nearly identical behavior regardless of the type of the photoabsorber in the device as the TiO2 and the RuOx layer are in all devices similar. Additionally, similar to the Sb2Se3 photocathode case, both Si and Cu2O photocathodes showed two increasing semi-circles after the photocurrent onset (Figure in the Supporting Information). Therefore, we fitted the Si and Cu2O photocathodes with the matryoshka circuit used for the Sb2Se3 photocathode, and the resistances and capacitances from the fitting of the EIS data are shown in Figure . Regarding the highest frequency RC element, we speculate that it results from artifacts (e.g. interference by the reference electrode and/or contact problem) without any relevance for the semiconductor junctions (the RHF was constant with respect to the applied potential regardless of the type of semiconductor and the light intensities, see Figure in the Supporting Information). In the Sb2Se3 case, the RHF is discernable from the Rrec1 while in some cases the two elements merged, which makes the fitting trickier (Figure in the Supporting Information). As the twooverlapping semicircles can lead to misinterpretation, care should be taken when there are two or more possible elements appearing at a similar frequency range (see Figure in the Supporting Information). Checking the Mott-Schottky plots and the corresponding doping density and flat band potential, obtained by fitting of the relevant semicircle in the EI spectra, shows if the values are realistic or not (and therefore if the equivalent circuit used for the fitting procedure was correct).