Measuring Carrier Concentration on the Back Side of Thin Film Solar Cells

The ability to profile and understand carrier concentration throughout thin film absorbers is important to advance solar cell technology. Here, the historical impediments of grain boundary potentials, lateral resistance, and high work functions to such measurements on polycrystalline solar cells are overcome by applying electrochemical capacitance-voltage profiling across the solar cell p-n junction and an electrolyte/semiconductor junction made at the back. Despite the presence of two junctions, modeling indicates that accurate carrier concentrations at the rear of the device can be measured under certain conditions. This is validated by experiments on CdTe solar cells.