Role of high series resistance in admittance spectroscopy of kesterite solar cells

Cu
₂
ZnSn(S, Se)
₄
(CZTSSe) solar cells suffer from parasitic resistance effects when decreasing the temperature. This effect can cause distortions in the admittance spectrum. We perform temperature dependent current-voltage (IVT) and admittance measurements on six different CZTSe devices with efficiencies between 4 % and 6 %. From IVT measurements we deduce a thermally activated series resistance. This activation energy agrees with an activation energy obtained from admittance measurements. The activation energy of the series resistance is identified with one of the capacitance steps in the C-f profile. The origin of the series resistance remains unclear, even though hints for a barrier are present.