A perovskite tandem is a two-story solar cell: a thin layer of perovskite on top, familiar silicon below. Each story catches its own part of the solar spectrum, and together they turn more light into electricity than silicon alone. For homes and business these are future panels that will give noticeably more energy from the same roof. Today these are lab records, not a product.
How it works
Sunlight is a mix of photons with different energies: blue ones carry a lot, red and infrared ones less. Silicon absorbs almost all visible light, but from each “rich” blue photon it takes exactly as much energy as it needs to free one electron, and the rest turns into heat. That is why silicon has a physical ceiling, and an ordinary panel turns 22–24% of sunlight into electricity.
Perovskite is a crystal with the same lattice as the mineral perovskite, named after the mineralogist Lev Perovski. For cells it is applied from a solution of lead, iodine and bromine compounds at a low temperature — in a layer many times thinner than a hair. The composition is tuned so that the top layer takes the blue and green part of the spectrum with smaller losses and lets red and infrared light through, down to the silicon. The two stories share the sun, and LONGi’s record for such a cell is 35.5%.
The main difficulty is durability. Silicon stands on a roof for years in rain and heat, while perovskite is sensitive to moisture, heat and ultraviolet light: the crystal slowly breaks down, and the cell loses power. Scientists are working out compositions, protective layers and sealed packaging, and learning to coat large areas evenly instead of tiny lab samples. For now, records are set on small cells, and there are no mass-market panels.
Where it already works
- Manufacturers’ labs: LONGi’s tandem cell record — 35.5%, July 2026.
- Durability testing of samples under sun, moisture and heat.
- Research into light, flexible cells for roofs where a heavy panel will not do.
What to consider
- There are no mass-market panels: check any “perovskite” panels on sale today especially strictly.
- The efficiency record is for a small lab cell; a large panel always scores lower.
- Service life on a roof has not yet been proven by years of operation — that is the main open question.
- If you need a system now, go with TOPCon: these panels are cheaper than ever.