Tandem Solar Cell
Multi-layer solar cell combining two semiconductor materials to utilise different light spectra and achieve higher efficiencies.
Also known as: Tandem Cell, Multi-Junction Solar Cell
What Is a Tandem Solar Cell?
A tandem solar cell consists of two solar cells stacked on top of each other with different band gaps. The top cell absorbs short-wavelength (high-energy) light, while the bottom cell utilises long-wavelength light. This way, a broader portion of the solar spectrum is converted into electricity.
Technology
The most promising combination is perovskite on silicon:
| Layer | Material | Band Gap | Absorbed Light |
|---|---|---|---|
| Top cell | Perovskite | ~1.7 eV | Blue, green |
| Bottom cell | Silicon (HJT/TOPCon) | 1.12 eV | Red, infrared |
Efficiency Potential
| Technology | Lab Record | Theoretical Limit |
|---|---|---|
| Silicon (single junction) | 26.8% | 29.4% (Shockley-Queisser) |
| Perovskite/silicon tandem | 33.9% | ~43% |
| Triple junction | 39.5% (III-V) | ~50% |
Development Status
Several companies (Oxford PV, Meyer Burger, LONGi) are working on commercialising perovskite-silicon tandem modules. First products are expected for 2025—2026.
Practical Tip
Tandem cells will be the next revolution in photovoltaics. They enable significantly more power per area and could supplement or replace standard silicon technology in the medium term.
Related Terms
Perovskite
Novel semiconductor material class for solar cells with high efficiency potential and simple manufacturing.
Solar Cell
Semiconductor device that converts sunlight directly into electrical current through the photoelectric effect.
HJT (Heterojunction)
Heterojunction cell technology combining crystalline and amorphous silicon, achieving very high efficiencies.
Efficiency
Ratio of usable electrical energy to incident solar energy -- indicates the effectiveness of a solar cell or system.