Stability of Cu(InxGa1-x)Se2 Solar Cells Utilizing RbF Postdeposition Treatment under a Sulfur Atmosphere: Article No. 2300052

Alkali halide postdeposition treatments (PDTs) have become a key tool to maximize efficiency in Cu(InxGa1-x)Se2 (CIGS) photovoltaics. RbF PDTs have emerged as an alternative to the more common Na- and K-based techniques. This study utilizes temperature-dependent current-voltage (JVT) measurements to study a unique RbF PDT performed in a S atmosphere. The samples are measured before and after 6 months in a desiccator to study device stability. Both samples contain Na and K which diffuse from the soda-lime glass substrate. A reference sample and a RbF + S PDT sample both show the development of a rear contact barrier after aging. The contact barrier is higher for the RbF + S PDT sample, leading to decreased current in forward bias. Series resistance is also higher in the RbF + S PDT device which leads to lower fill factor. However, after aging the reference sample has a larger decrease in open-circuit voltage (VOC). Ideality factor measurements suggest Shockley-Read-Hall recombination dominates both samples. VOC versus temperature and a temperature-dependent activation energy model are used to calculate diode activation energies for each sample condition. Both techniques produce similar values that indicate recombination primarily occurs within the bulk absorber.