Methods for resistivity and thickness measurements of high resistivity interfacial layers in photovoltaic TCO multilayers

Transparent conductive oxide (TCO) layers for high-efficiency thin-film photovoltaic modules consist of several layers with different thickness and electric resistivity. In particular SnO2-based TCOs consist of a conductive indium tin oxide (ITO) base layer and a thin, highly resistive interfacial layer. These interfacial layers are crucial for the performance of the solar cells due to their impact on series resistance and band gap matching. Process-induced degradation may additionally change the structural and electric properties of the highly resistive interfacial layer between absorber material and ITO. This paper presents a method to measure the resistivity of the highly resistive interfacial layer by a modified transfer-length measurement (TLM) together with depth profiling and cross sectional thickness measurements with nm accuracy.