Investigation of CdTe solar cells via capacitance and impedance measurements

Two CdTe solar cells with very different IV-characteristics were analysed u sing impedance spectroscopy (IS) and capacitance-voltage (CV) measurements at different temperatures and under dark and illuminated conditions, The tw o samples were distinguished by different durations of the nitric-phosphori c (NP) etching process applied before back contact deposition. The cell wit h a short etching time (30 s) shows a strong roll over in the forward bias region, and the cell with the surface that was etched for a longer time (3 min) showed a very strong decrease of the roll-over and a better fill facto r. The results show that the etching process dramatically changes the CV ch aracteristics, the resulting CdTe effective doping concentration and that t his change can be correlated to different equivalent circuits obtained by t he fitting of the impedance spectra of the two samples. O 2001 Elsevier Sci ence B.V. All rights reserved.