Analysis of the temperature characteristics in polycrystalline Si solar cells using modified equivalent circuit model

We have evaluated the influence of grain boundaries on the temperature dependence of cell performance using a modified 2-diode equivalent circuit model. In this model, microscopic inhomogeneity of resistivity at or near grain boundaries can be taken into consideration. The calculated results by the modified 2-diode model agreed well with the measured current-voltage curves, and the validity of the fitting parameters in this model was discussed. One of the fitting parameters, r is defined as the ratio of the recombination area, in which the recombination of minority carriers is pronounced. At 20degreesC, r of the polycrystalline Si cell was larger than that of the single-crystalline Si cell. However, the difference in r between them became negligible at temperatures above 80degreesC. These dependences were explained by considering the behavior of the free carriers in the recombination centers.