Investigation of Dark Heat and Light Soaking Treatment on Cu(In,Ga)Se2 Solar Cells using Impedance Spectroscopy

Cu (In,Ga)Se
₂
solar cell material was measured by impedance spectroscopy before and after 1000 hours of 85 °C dark heat treatment to investigate the impact of reducing the back electrode pre-selenization. Each condition was measured before and after 16 hours of light soaking at 1 sun. The impedance spectra in forward bias typically show a primary arc interpreted as recombination in the junction and a smaller arc at high frequencies interpreted as thermionic emission across a barrier. Recombination in the junction decreases with damp heat treatment for reduced back contact pre-selenization, but increases after light soaking for all conditions. Activation energies for the back contact barrier range between 90 meV and 174 meV depending upon the stress and pre-selenization conditions.