Interrogating Dominant Recombination Pathways in CdTe Solar Cells Using Wavelength-Dependent External Radiative Efficiency Measurements

External radiative efficiency (ERE) measurements are increasingly being used by the CdTe community to identify sources of loss in these devices. So far, ERE has narrowly been applied to determining the implied open-circuit voltage (iV
OC
) throughout processing and determining the selectivity of contacts by comparing iVoc to measured open-circuit voltage (V
OC
). These applications fail to address more specific questions about the relative importance of the primary recombination channels in CdTe devices. Here, we simulate the Voc of CdTe devices under different monochromatic illumination and find that ERE should be able to distinguish differences in iV
OC
that correspond to differences in the location of the limiting recombination channel. The intensity dependence of the difference in iV
OC
between two wavelengths further refines the possible conclusions, as do back-illuminated ERE simulations. These principles are applied to wavelength- and intensity-dependent ERE measurements of a set of CdTe solar cells with purposefully varied front and back interface qualities. Experimental data shows agreement with simulation in several ways, however a more thorough treatment will be necessary to identify the most effective implementation.