Teaching solar cell I-V characteristics using SPICE

The basic equivalent circuit of a p-n junction solar cell is most commonly represented as consisting of a current source in parallel with two diodes and two parasitic resistances. The output of a solar cell is measured by obtaining the current-voltage (I–V) characteristics for different illumination intensities, and various parameters are extracted from these characteristics. Because the nature of the information derived from these characteristics is not obvious to the beginning students in photovoltaics, a simulation using SPICE was utilized to explain three solar cell I–V characteristics—dark I–V, illuminated I–V, and open circuit voltage versus the short circuit current (illumination intensity). Students can construct a solar cell and study the effect of the diode and parasitic parameters on the three output I–V characteristics. Series and parallel combinations of solar cells for arrays and modules using bypass diodes are demonstrated using SPICE as educational tools for understanding the role of bypass diodes.