To confirm our assumptions regarding the photocurrent mechanism, we irradiated each electrode individually (Figure ), as opposed to irradiating the entire mat uniformly as when the above measurements were taken, while recording the current response at 1.5 V (Figure ). To do so, we used a longer inter-electrode distance of 8 mm. Whereas placing the illumination beam above the anode resulted in a slight increase in current, the opposite configuration (above the cathode) resulted in a sharp decrease. Moreover, this reduction was more prominent than when the beam was located in the middle of the mat. The vast difference in the photocurrent behavior that can be attributed only to the location of the illumination strongly validates our suggested mechanism. Under high bias, the illumination of the anode does not promote new favored electron pathways (Figure ). However, irradiation near the cathode allows the excited electrons to flow from the conduction band to the electrode (Figure ). As we hypothesized, the overall photocurrent in the high voltage regime is dominated solely by processes next to the cathode. Above, we described the modulation of the observed photocurrent generation of our fully doped mat as a function of applied bias and the location of the irradiated area. We now address the use of a gradient-doped mat. As shown in our previous study, the simplicity of our molecular doping method enables easy control of the dopants' concentration. In our study, we utilized this advantage to form a gradient-doped mat, one end of which is fully doped and the second end is non-doped. This approach breaks the symmetry in our system and allows the Chl molecules to interface only with a certain electrode, depending on the configuration. Figure shows the position of the gradient-doped mat, where the Chl was next to the anode and an 0-0.3 V voltage was applied. In this setup, the irradiation (of the entire sample) resulted in an increase in the current. However, when we inverted the orientation of the mat with respect to the electrodes, a decrease in current was observed for the same bias regime (Figure ). We can use a band alignment similar to that described above to explain these results (Figure ). In zero bias mode, the potential on both electrodes is equal, and therefore, our suggested model predicts that an excited electron will flow from the conduction band to the nearby electrode. When the Chl is located next to the anode, the excitation causes electrons to shift in the current direction. In the opposite case, when the Chl is located next to the cathode, the excited electrons flow in the reverse direction, and hence, the chromophore's location dictates the photocurrent direction. We further used this symmetry-breaking gradient-doped mat to construct a bias-dependent photocurrent device. As the bias polarization determines the anode and cathode, we anticipated obtaining a similar performance by simply flipping the bias polarization. To examine this idea, we used the same configuration described above with the doped part next to the anode and changed the applied bias from a positive 0.1 V to a negative -0.1 V (Figure ). As shown in the figure, the two conditions offer a vital difference in the photocurrent generated: under a positive bias, a rise in current, and under the negative bias, a decrease in current. Hence, unlike the fully doped mat, where a change in voltage direction produces a mirror image of the current (Figure ), when the gradientdoped mat is used, the voltage polarization determines the photocurrent direction. What distinguishes our system compared to any natural system is the flexibility in choosing the light-harvesting molecule within the protein. Accordingly, in our final section, we show the results of an experiment in which we switched from using Chl as the light-absorbing chromophore to using protoporphyrin IX (PPIX) as the dopant. As when Chl was used, we observed a significant negative photocurrent upon light excitation at high biases and a switch in the photocurrent polarity when the low-voltage regime was reached (Figure ). The only difference in the PPIX-doped mat from the Chl-doped one is the observed bias of the photocurrent polarity switching, where in the Chl-doped mat it was around 0.9 V (Figure ) and in the PPIX-doped mat around 0.5 V. The difference in the switching bias is indicative of the different positions of the valence band between Chl and PPIX (as explained for Figure ). We further confirmed the recurrence of the negative photocurrent phenomenon by applying a constant voltage of 1 V while repeatedly turning the light on and off in cycles (Figure ). We also conducted the same experiment again, except that initially the light was switched on, which showed the same trend, i.e., an increase in current when the light is switched off (Figure ). Finally, we also demonstrated that the light intensity can be used as a gating source for controlling the generated photocurrent (Figure ), whereas the higher the light intensity, the larger the photocurrent response.