Tandem solar
Two light absorbers stacked together, each catching a different part of the sunlight.
How tandems work
Sunlight contains a range of colours with different energies. A single material can only use part of that range efficiently. A tandem cell stacks two materials: the top layer absorbs higher-energy light and lets the rest through to the bottom layer, which absorbs lower-energy light.
Why perovskite on silicon
Silicon is cheap and proven; perovskite can be tuned to absorb the higher-energy part of sunlight that silicon handles poorly. Together they have set laboratory records well above what silicon alone can achieve. Multi-junction cells made from other materials already power satellites, but they are far too expensive for ordinary panels.
Advantages and limitations
Advantages
- Highest efficiency potential of any mass-market approach
- Builds on existing silicon factories
- More power from the same roof area
Limitations
- Inherits perovskite durability questions
- More complex manufacturing
- Not yet widely available
Current development
Manufacturers are running pilot lines for perovskite-silicon tandem panels. Proving their long-term reliability is the key step toward mass production.
Further reading
- Multi-junction solar cell (Wikipedia)How stacked cells work
- NREL best research-cell efficiency chartCurrent tandem records