Reliable Method for the Measurement of Diffusion Capacitance in Solar Photovoltaic Cells

The dynamic parameters of solar photovoltaic (PV) cells, especially the intrinsic diffusion capacitance, are important when they are connected to switched-mode converters or are used in switched-capacitor structures. Furthermore, the dynamic parameters can be used for the minority carrier lifetime measurement of solar PV cells. Among the different small-signal measurement methods suggested in the literature, voltage-biased methods are common. However, diffusion capacitance is an exponential function of the cell voltage over the temperature. Thus, for a given voltage, the diffusion capacitance varies greatly by temperature. In this paper, a current-biased small-signal measurement method is investigated which can not only measure the diffusion capacitance of solar PV cells, but also the parasitic inductance, and the quality factor of the cells. Additionally, different external inductors are used to resonate the solar PV cell at different test frequencies. As a result, the diffusion capacitance, the parasitic inductance, and the quality factor are measured at different frequencies. The method is demonstrated through a hardware prototype.