Since our proposed mechanism involves anodic photocurrent generation (in a similar fashion to an electrochemical setup), a quencher is required to serve as the source for hole recombination. While it is impossible to pinpoint the exact quencher in our protein matrices, the presence of many functional groups of the protein together with a large water content within the protein-based solidstate matrix (up to 150 wt.% of water) can be considered as the source of the quenching process. To have an insight into the role of the protein as the quencher of the process that also allows the reversibility of the process, we have performed two control experiments. The first is to deposit on the electrodes a solution of solvated BSA following the integration of Chl into them. This control experiment has the same 'ingredients' as our main study, but not in a free-standing solid-state biopolymer configuration, thus, it is resembling 'common' photoelectrochemical studies. In this control experiment, we can see a similar drop in current at high biases (Figure ) that is in line with the discussed results with the Chl-doped BSA mat (Figure ), but the reversibility upon returning to dark was much slower in the solvated protein configuration in comparison to the mat configuration, which can be ascribed to diffusion-limited processes. The second control experiment is to deposit Chl without protein on our device (in an aqueous solution), thus directly targeting the role of the protein in the process. As can be observed in Figure , without the protein, the Chl can also induce the negative photoresponse at higher biases, albeit with a smaller magnitude. However, unlike the experiment with the protein mat or with solvated proteins, using only Chl is resulting in a non-reversible process, meaning that after returning to dark conditions, the current did not go up again. Accordingly, we can conclude that the protein has a major role in the quenching process of donating a hole and bringing the system to its initial state (before the light excitation).