Calculation of the thermodynamic voltage limit of CdSeTe solar cells

The first step to understand the origin of losses in any photovoltaic solar cell is to determine the fundamental thermodynamic efficiency and voltage limits of such a device. In this contribution, we detail techniques to calculate the voltage limit in the case of cadmium selenium telluride (CdSeTe) solar cells, and how approaches based on bandgap alone—i.e., the Shockley-Queisser approach with step-function absorptance—can overestimate the thermodynamic open-circuit voltage limit $V_{oc,ideal}$. This is particularly true for arsenic-doped samples, which tend to exhibit below-bandgap absorptance.