Analysis of the Current-voltage Curves of a Cu(In,Ga)Se2 Thin-film Solar Cell Measured at Different Irradiation Conditions

We analyze the current density - voltage (J - V) curve of a Cu(In,Ga)Se-2 (CIGS) thin-film solar cell measured at different irradiation power densities. For the solar-cell sample investigated in this study, the fill factor and power conversion efficiency decreased as the irradiation power density (IPD) increased in the range of 2 to 5 sun. Characteristic parameters of solar cell including the series resistance (r(s)) the shunt resistance (r(sh)), the photocurrent density (J(L)), the saturation current density (J(s)) of an ideal diode, and the coefficient (C-s) of the diode current due to electron-hole recombination via ionized traps at the p-n interface are determined from a theoretical fit to the experimental data of the J V curve using a two-diode model. As IPD increased, both r(s) and r(sh) decreased, but C-s increased.