Electron beam induced current in photovoltaics with high recombination

A model for interpreting electron beam induced current (EBIC) measurements is presented, which applies when recombination within the depletion region is substantial. This model is motivated by cross-sectional EBIC experiments on CdS-CdTe photovoltaic cells (prepared by cleaving, or focused ion beam milling). The experimental results clearly show that the maximum efficiency of carrier collection is less than 100 % and varies throughout the depletion region, contrary to the assumptions of most models used to interpret EBIC data. We describe a model which relaxes these assumptions by including recombination in the depletion region. We find that our model can reproduce experimental results only if the mobility-lifetime product μτ is spatially varying within the depletion region.