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

Abstract

We analyze the current density - voltage (J - V) curve of a Cu(In,Ga)<TEX>$Se_2$</TEX> (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 (<TEX>$r_s$</TEX>), the shunt resistance (<TEX>$r_{sh}$</TEX>), the photocurrent density (<TEX>$J_L$</TEX>), the saturation current density (<TEX>$J_s$</TEX>) of an ideal diode, and the coefficient (<TEX>$C_s$</TEX>) 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 <TEX>$r_s$</TEX> and <TEX>$r_{sh}$</TEX> decreased, but <TEX>$C_s$</TEX> increased.