29th November 2025

LONGi sets new 33.4% solar efficiency record

In yet another breakthrough for solar photovoltaic technology, a new flexible perovskite–silicon tandem has achieved a certified world record efficiency of 33.4%.

LONGi, a major photovoltaics company founded in China in 2000, has announced a significant advance in solar cell performance, setting a new world record efficiency with a flexible perovskite–silicon tandem device. Certified at 33.4% by the US National Renewable Energy Laboratory (NREL), this result is the highest percentage ever recorded for a flexible solar cell of any kind. The research is published this month in Nature and highlights how rapidly this next generation of solar cells is evolving. It also places these ultrathin devices within striking distance of the theoretical limits previously associated with rigid laboratory cells.

"Tandem" refers to solar cells that combine two or more sub-cells with different properties into a single unit to absorb a broader range of the light spectrum, achieving higher efficiency than a single-junction cell would. In recent years, perovskite/crystalline silicon tandems have emerged as one of the most promising future concepts. LONGi's new design is based on a high bandgap perovskite top layer, with a crystalline silicon bottom layer. Sandwiched between these is a recombination layer of nanocrystalline silicon oxide and intrinsic amorphous silicon, connecting the two sub-cells electrically.

The top cell absorbs the higher energy portion of sunlight, while the silicon beneath captures the lower energy light that passes through, allowing the two layers to work together as one highly efficient unit. LONGi's researchers used refined deposition methods to minimise defects, improve interfacial coupling, and align the current between both sub-cells.

In addition to a small-scale (1 cm²) demonstration at 33.4% efficiency, the team produced a commercial-size, wafer-level version (260 cm²), which achieved 29.8% efficiency under Fraunhofer ISE certification. This marks the first time that a flexible crystalline silicon perovskite tandem has been recognised with an internationally certified world record, demonstrating progress not only in small laboratory cells but also at scales more directly relevant to manufacturing.

Notably, the bottom layer of crystalline silicon is just 60 micrometres (μm) in thickness. Traditional silicon wafers have thicknesses of 120–200 μm and are usually considered rigid and brittle. But somewhat counterintuitively, the atomic structure of silicon allows for a certain degree of elastic deformation. Once the material becomes ultrathin, it gains flexibility because the stress from bending is no longer high enough to break the crystalline lattice. Ultrathin silicon wafers can therefore meet the deformation requirements for lightweight, flexible devices. LONGi's device can be bent to a radius of 1.5 cm and folded repeatedly without mechanical failure. In other words, it could be bent around an object roughly the size of a US half dollar coin (or a £2 coin), while remaining fully functional and without cracking. Its power-to-weight ratio is 1.77 W per gram, tens of times higher than typical commercial flexible panels.

"The modified tandem solar cells demonstrate good durability, retaining over 97% of their initial power conversion efficiencies after 43,000 bending cycles," according to LONGi.

Future applications may include vehicle-integrated photovoltaics, the study authors suggest, thanks to the combination of high efficiency, low weight, and bending fatigue resistance. Lightweight but powerful modules could be wrapped around car roofs, lorry trailers, or trains, for example, providing a steady supply of onboard electricity without adding significant mass. Similar designs mounted on drones, high-altitude platforms, or spacecraft would help to extend flight times and mission lifespans, especially in environments where replacing or refuelling power systems is difficult.

Rigid perovskite–silicon tandems have been steadily improving for nearly a decade, but their flexible counterparts have progressed even faster – rising from the low-20% range to now 33.4% efficiency in barely 18 months. This rate of advancement reflects how quickly researchers are refining materials, interfaces, and fabrication methods.

Further gains might begin to slow and reach an asymptote as the technology converges on its theoretical upper limit, believed by experts to be about 40%. Extrapolating the current trend suggests that lab-scale devices could approach this point as soon as the early 2030s. Achieving such a figure would be a major milestone for the industry. Flexible solar cells operating near this physical boundary would combine extraordinary performance and superb mechanical versatility, opening the door to new classes of high-efficiency commercial systems in the next decade.

Comments »

If you enjoyed this article, please consider sharing it: