Characterization of nanocrystal-ink based CZTSSe and CIGSSe solar cells using voltage-dependent admittance spectroscopy

Voltage-dependent admittance spectroscopy has been applied nanocrystal-ink based CZTSSe and CIGSSe solar cells to understand the origins of admittance signatures characterized for devices fabricated from this method; devices considered here have demonstrated champion device efficiencies of 9.0% and 14.2%, respectively. Two admittance signatures characterized for CZTSSe have been attributed to two bulk defect levels; however, a single admittance signature characterized for CIGSSe is expected to be due to a Schottky barrier at the back contact. Additionally, punch-through due to the free carrier freeze-out at low temperatures only occurs in CZTSSe, which suggests a shallower defect contributing to the carrier density in CIGSSe than CZTSSe. Results are compared with that reported for CIGSSe and CZTSSe devices fabricated from other processing techniques.