Interpretation of admittance signatures in Cu(In,Ga)Se2 solar cells

In this work we use numerical simulations to investigate the origin of the capacitance step commonly observed in thermal admittance spectra of CIGS solar cells. We analyze what are the effects on the frequency- and temperature dependent capacitance curves of: (a) the conduction band offset at the CdS/CIGS interface; (b) an interfacial defect distribution between CIGS and CdS; (c) a Schottky barrier at the rear contact; (d) a grain-boundary (GB). We extract the depletion region width from the simulated capacitance step height and compare it with experimental data.