Direct evidence for grain boundary passivation in Cu(In,Ga)Se<sub>2</sub> solar cells through alkali-fluoride post-deposition treatments.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31484943.
- Also identified by DOI 10.1038/s41467-019-11996-y and PMC identifier 6726603.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The properties and performance of polycrystalline materials depend critically on the properties of their grain boundaries. Polycrystalline photovoltaic materials - e.g. hybrid halide perovskites, copper indium gallium diselenide (CIGSe) and cadmium telluride - have already demonstrated high efficiencies and promise cost-effective electricity supply. For CIGSe-based solar cells, an efficiency above 23% has recently been achieved using an alkali-fluoride post-deposition treatment; however, its full impact and functional principle are not yet fully understood. Here, we show direct evidence for the passivation of grain boundaries in CIGSe treated with three different alkali-fluorides through a detailed study of the nanoscale optoelectronic properties. We determine a correlation of the surface potential change at grain boundaries with the open-circuit voltage, which is supported by numerical simulations. Our results suggest that heavier alkali elements might lead to better passivation by reducing the density of charged defects and increasing the formation of secondary phases at grain boundaries.