LONGi just pushed tandem solar efficiency to a record 35.5%

Signals Inbox·July 19, 2026·Solar

LONGi says its silicon-perovskite tandem cell has reached a certified 35.5% efficiency, a new lab record. The bigger tension is the gap it opens over silicon alone: top silicon cells are still near 27%, while commercial tandem modules remain closer to the mid-20s. The science is moving much faster than the factory.

Q1Where does the record come from?

LONGi is the primary source for the 35.5% claim. Its official updates are published through the LONGi news center. Independent research-cell records are tracked on the NREL efficiency chart. The exact certificate and test details matter because record cells are measured under tightly controlled lab conditions.

Q2What actually happened?

LONGi stacked a perovskite cell on top of a crystalline silicon cell and converted 35.5% of incoming light into electricity. The two layers catch different parts of the light spectrum, so less energy is wasted than in a normal silicon cell. That is the basic reason tandem cells can move beyond silicon's practical ceiling.

Q3How big is 35.5%?

It is roughly eight percentage points above the best single-junction silicon cells, which sit near 27%. That is a large jump in solar, where tiny gains can reshape panel output, land use, installation costs, and project economics. But it is still a small research cell, not a mass-market panel shipping at 35.5%.

Q4Is this close to what buyers can get?

Not yet. Standard commercial silicon panels are usually around 20% to 23% efficient. Oxford PV has shipped tandem modules around 25%, and its commercial-size record reached 26.9%. LONGi's 35.5% result shows the technical ceiling is rising fast, but factories still need to close a gap of roughly nine to ten points.

Q5What is still blocking scale?

Durability, coating consistency, large-area manufacturing, yield, and cost. Perovskites can degrade under heat, moisture, and long outdoor exposure. A record made on a small lab cell only matters commercially if manufacturers can reproduce it across full-size modules for decades, with low failure rates and cheap production.

Q6Why does this matter now?

Because tandem solar is crossing from science project into an industrial race. Oxford PV has already shipped commercial modules, while Chinese giants such as LONGi and Trina have the factories, supply chains, and scale to move much faster once the process works. The real question is no longer whether tandem cells beat silicon. It is who can manufacture them reliably first.

Q7So what should we watch next?

Watch module-size efficiency, production yield, warranty length, and factory capacity. A 30% commercial module with a long warranty would matter far more than another tiny lab record. LONGi has proved the performance race is still accelerating. Now it has to prove that 35.5% can survive the jump from a test bench to millions of rooftops.