Superior solar through anion engineering
Careful chemical tuning could offer a way to create ultrahigh-efficiency solar cells that combine two photovoltaic materials in a single structure.
Perovskites are a new photovoltaic technology with light-harvesting efficiencies that rival silicon cells. Rather than compete with silicon technology, a perovskite layer could be coated onto silicon, forming a tandem solar cell that captures more solar energy than either photovoltaic material could achieve alone.
The ideal perovskite for a tandem cell would be made from a mixture of iodine and bromine, to tune its light-capturing ability to perfectly complement silicon’s solar absorption. However, exposure to sunlight tends to cause the iodine and bromine to migrate through the perovskite, reducing its working lifetime.
A team that included KAIST scientists has used anion engineering to develop a separator substance that keeps neighbouring perovskite sheets apart, limiting migration. An optimized anion mixture gave a stable tandem cell that captured solar energy with an efficiency has high as 26%.
- Science 368, 155–160 (2020). doi: 10.1126/science.aba3433