CEA and WattByWatt Hit 28% Efficient Tandem Solar Record Milestone

• WattByWatt’s air-processed perovskite ink helps France’s CEA hit 28 % efficiency in a tandem perovskite-silicon cell, edging closer to scalable next-gen solar panels.

Canadian start-up WattByWatt and France’s energy-research powerhouse CEA have taken a decisive step toward next-generation photovoltaics, reporting a certified 28 % power-conversion efficiency for a prototype tandem perovskite-on-silicon solar cell. The result, achieved on a 9-cm² device, underlines the rapid progress of perovskite technology and its growing readiness for mass production.

From IoT mini-modules to utility-scale ambitions

Founded in Montréal in 2020, WattByWatt cut its teeth producing single-junction perovskite mini-modules designed to harvest indoor light for smoke detectors, smart locks and other low-power IoT devices. The company’s differentiator is a proprietary ink that lets manufacturers deposit perovskite layers in ambient air via a scalable wet-coating process—eliminating the costly inert-atmosphere chambers most rivals still need.

CEA’s tandem expertise meets Canadian chemistry

The French Alternative Energies and Atomic Energy Commission (CEA) has been at the forefront of tandem research for nearly a decade, repeatedly pushing the world-record envelope. Engineers at CEA-INES, the organisation’s solar R&D institute, integrated WattByWatt’s air-stable ink into their established two-terminal tandem architecture. The resulting device hit the 28 % mark on first pass, a figure that rivals the best lab results produced with far more complex vacuum-based techniques.

Why it matters

Perovskite-silicon tandems promise to shatter the single-junction efficiency ceiling that has capped mainstream panels at around 24 % for years. Yet scaling fragile perovskite films from millimetre-scale lab samples to square-metre commercial modules has been the industry’s sticking point. WattByWatt’s air-processed approach, validated on CEA’s pilot line, hints at a manufacturing route compatible with roll-to-roll coating, lower capital expenditure and fewer production bottlenecks.

What’s next

The partners will now focus on stability testing, module-level upscaling and cost-of-ownership analyses—key prerequisites for bankability. If those hurdles are cleared, the technology could move from pilot to pre-commercial lines later this decade, giving European and North-American manufacturers a realistic path to higher-efficiency panels without relying on Asian supply chains.

For an industry racing to cut costs while squeezing every extra watt from each square metre, a robust 28 % tandem produced in room air is more than a scientific footnote—it is a glimpse of solar’s near future.