Considering the material and manufacturing process of solar cells, the internal impedance of silicon wafers and the contact of electrodes will cause the series resistance Rs, the incompleteness of the PN junction will cause the parallel resistance Rsh, and the PN junction has junction capacitance CJ. Under a certain light intensity, the photocurrent of the solar cell does not change with the working state. It can be regarded as a constant current source in the equivalent circuit, the terminal voltage, in turn, is biased toward both ends of the PN junction, generating a dark current in the opposite direction to the photocurrent.