The flip in the photocurrent generation can be explained by considering the valence and conduction band alignment with respect to the electrodes. As mentioned above, to date, most of the photocurrent generation studies in which proteins were used involved an electrochemical setup. However, because of our solid-state configuration, it is essential to consider the different processes next to each of the two electrodes. We previously showed that a porphyrin-doped mat has a p-type carrier behavior. The hole transfer (or hole accepting) capabilities of the Chl molecules hint at the involvement of an anodic photocurrent mechanism rather than a cathodic one. Regardless of the voltage used, the process starts with a photon exciting the Chl and creating an electron-hole pair. At low voltages (Figure ), the excited electron can flow from the conduction band to the anode and thus increase the current. However, above a critical voltage, which from our experiments we estimate to be around 0.9 V (Figure ), the anode potential is lower than the valence band of our material. In the latter case, there is no preference for the excited electrons, and thus, no increase in current should occur.