The photocurrent responses were investigated for the biomolecular bulk-hetero junction of chlorophyll α (Chl-α) and
1-(3-methoxycarbonyl)-propyl-1-phenyl-1-phenyl-(6,6)C<sub>61</sub> (PCBM) in the temperature range between 300 K and 1.5 K
under the magnetic field up to 8 T. The chopped-light photocurrent decreases on lowering the temperature. Below 10 K,
photocurrent decrease was observed under the applied magnetic field. Decay of the photocurrent observed at 10 K was
ascribed to the formation of the charged trap under light irradiation. The magnetic field effect (MFE) observed in this
device was found to be very similar to that observed in P3HT:PCBM bulk-hetero junction at low temperatures.