On the Use of Rau's Reciprocity to Deduce External Radiative Efficiency in Solar Cells

Rau's reciprocity relation has been used to deduce the external radiative efficiency of a wide variety of solar cells using just standard solar cell measurements, but it is based on a number of assumptions, some of which may not be valid for typical thin-film solar cells. In this paper, we use rigorous optical simulations, coupled with carrier transport simulations, to examine some common thin-film solar cells. The results provide guidance on when the Rau relation can be used, why it can fail, and the magnitude of the errors that can be expected in practice.