Approach to determining the limiting recombination mechanism in CdTe-based solar cells

Determining exactly how the performance of a thin-film photovoltaic device is limited by a particular recombination mechanism can be difficult, particularly in the case of CdTe solar cells. As a result, efforts are being made to improve all parts of the device without good knowledge of which improvements are necessary. To understand where the device limitation is, the recombination current densities of at least one on of the interfaces must be known. Here, we present a method to determine which recombination mechanisms is limiting. First, back illuminated quantum efficiency measurements are used to determine the key parameters of the back interface – the back surface recombination velocity and the band bending near the back surface. Once these back interface parameters are determined, the recombination current densities can be calculated for a front illuminated device to determine the limiting mechanism. The validity of the approach is tested using previously reported data. •Approach to determine surface recombination velocity and band bending at back of device using backside quantum efficiency.•Use values for back interface to determine recombination current densities of front illuminated device at open circuit.•Can identify location of limiting recombination in devices.•Demonstrated approach using high bifacial CdTe solar cell.