Surface Photovoltage Spectroscopy to Evaluate Rear Passivation Strategies in CdTe Photovoltaics

We present developments in surface photovoltaic spectroscopy (SPS), aimed at characterizing passivation strategies for CdTe cell interfaces, particularly the rear contact. Effective rear contact passivation has been predicted to increase device efficiency by as much as 3.5% when coupled with a hole selective contact. We demonstrate how SPS is a critical tool in evaluating novel solutions to eliminate voltage loss at interfaces. We examine the effect of known wet etchant strategies on SPS signal, correlating and contrasting the information gained with that available via TRPL. We also explore passivating interface layers in CdTe and Si based devices. SPS signals are evaluated via SCAPS 1D modeling and analytical modeling and the effects of surface recombination velocity, band bending, and recombination in bulk and SCR are extracted.