These CIGS cells are flexible and require only a fraction of the material used for silicon solar cells. Combining them with perovskite significantly improves their efficiency.https://www.notebookcheck.net/Record-efficiency-achieved-by-thin-film-solar-cell.957560.0.html
It's a record for this tandem combination. But it is still not the best record for a tandem configuration. As for costs and durability, separate issues as noted. But progress.
Yeah, anything using perovskite but not mentioning on how they intend to keep the cell from degraging is likely just gunning for top performance. Like, gunning for a land speed record will not net you a perfect commuter car. Still, it is encouraging to see progress in the field.