Performance Stabilization of CdTe PV Modules Using Bias and Light

Reversible performance changes due to light exposure frustrate repeatable performance measurements on CdTe photovoltaic modules. It is common to use extended light exposure to ensure that measurements are representative of outdoor performance. We quantify the extent to which such a light-exposed state depends on module temperature and consider voltage bias in the dark to aid in stabilization. We evaluate the use of dark forward voltage bias to bring about a performance state equivalent to that obtained with light exposure, as well as to maintain a light-exposed state prior to standard test condition (STC) performance measurement. Our results indicate that the most promising method for measuring a light-exposed state is to use light exposure at controlled temperature followed by prompt STC measurement with a repeatable time interval between exposure and the STC measurement.