Fossil Fuels Can’t Win Against New Perovskite-Silicon Solar Cells

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Lower-costing, higher-performing perovskite solar cells are finally beginning to emerge from the laboratory, further cementing the Sun into position as the most economical, accessible, and abundant source of new kilowatts for the global grid — regardless of what US President Donald Trump has to say about it. Some perovskite solar cells are already market-ready, even as searchers continue to outline pathways for further improvement.

The Long Road To Perovskite Solar Cells

CleanTechnica has been following the perovskite story for a dozen or so years (here’s an early example), as research teams around the world have worked to transform the finicky, brittle material into next-generation, high performing solar cells that cost less than their conventional counterparts.

In recent years the focus has shifted into a tandem format, in which perovskite is layered with silicon. The perovskite layer is relatively inexpensive and easy to fabricate at high volume, pushing the overall cost of the solar cell down while pushing up its ability to convert sunlight to electricity.

As for how much more solar conversion is possible with a tandem perovskite solar cell, that’s a good question. A 1960s-era formula called the Shockley-Queisser limit sets the conversion efficiency for a single junction solar cell at 33.7%. In 2023 the leading Chinese firm LONGi topped that, reporting a record-breaking conversion efficiency of 33.9% for a perovskite-silicon tandem solar cell.

43% Is The (Theoretical) Limit Of Perovskite Solar Cells

That was just for starters. Earlier this year LONGi reported a conversion efficiency of 34.85%, another record-breaker that brought the firm within shouting distance of the theoretical limit of 43% for the tandem formula.

Scaling up those next-generation solar cells from lab samples and launching them into the market is a next-level task. However, researchers at Hong Kong Polytechnic University are among those anticipating commercial applications in topping the 30% range.

In their new study, “Towards efficient, scalable and stable perovskite/silicon tandem solar cells” (published in the journal Nature Photonics), the PolyU team took note of the potential for improvement. “Despite recent power conversion efficiency values nearing 35%, perovskite/silicon TSCs still exhibit a considerable efficiency deficit relative to their theoretical upper limit,” they wrote.

“Scientific and technological challenges related to the long-term operational stability and scalability must also be addressed for this technology to be commercialized,” they added.

“The team has conducted a comprehensive analysis of TSC [tandem solar cell] performance and provided strategic recommendations, which aim to raise the energy conversion efficiency of this new type of solar cell from the current maximum of approximately 34% to around 40%,” PolyU further explained in a press release

PolyU Professor Li Gang, the school’s Chair Professor of Energy Conversion Technology, also drew attention to the gap between laboratory results and real world applications. “While lab-scale devices have shown impressive efficiency advancement, further efforts are needed to improve their reliability, including minimising efficiency losses from small-area devices to large-area modules,” Gang explained.

Gang also underscored the key role of manufacturing systems. “Special focus should also be given to ensuring that the manufacturability of materials and methods aligns with industrial standards,” Gang said.

Making It Over The Finish Line

The PolyU researchers recommend addressing ongoing challenges in perovskite stability and manufacturing processes, along with adopting an accelerated testing regimen outlined by the International Electrochemical Commission.

They also indicated that the supply chain continues to present a sustainability issue. “Additionally, while perovskite raw materials are relatively low-cost, the use of rare elements and heavy metal lead in most cell designs raises significant environmental and regulatory concerns,” PolyU notes.

“The research therefore advocates for the development of sustainable alternatives, along with efficient recycling or lead sequestration strategies to enable viable commercialisation,” the school emphasizes.

While those loose ends are tied up, some solar manufacturers are already satisfied that tandem perovskite-silicon technology beats silicon alone, even without marching towards the 43% limit.

The US startup Tandem PV, for example, has been assembling the funds to begin mass production of solar panels featuring tandem perovskite-silicon solar cells. The company claims a solar conversion efficiency of 28% for its panels, making them “30% more powerful than the average silicon solar panel.”

In an interview with the business news organization Pulse 2.0 in August, Tandem CEO Scott Wharton also explained how the cost savings works out. “Our panels generate more power at a similar price per watt, dramatically reducing the levelized cost of energy (LCOE) by lowering land, labor, and balance-of-system expenses,” he said.

“Unlike traditional power plants that take years to build, solar farms can be deployed in months, aligning with the fast pace of AI growth,” he also noted.

Perovskite-Silicon Tandem Solar Cells: Follow The Money

In October of 2024, Tandem PV received a $5.2 million grant from the US Department of Energy to speed it on the way to volume manufacturing. If the grant survived the Trump administration’s renewable energy chopping block, that would be something of a miracle. When business news organization Pulse 2.0 interviewed Tandem CEO Scott Wharton in August he referenced the Energy Department grant, though the grant summary currently posted at usaspending.gov indicates only part of the funds were outlayed as of September.

Meanwhile, Tandem more than made up the difference in March of this year, when the company nailed down $50 million in Series A funding and debt, earmarked for the construction of a commercial-scale factory. The activity was spearheaded by the US firm Eclipse with a long list of participants including Constellation Energy, Planetary Technologies, Uncorrelated Ventures, and Trellis Climate, among others.

In July, the California Energy Commission also provided Tandem PV with a $4 million grant to help shorten the firm’s manufacturing timeline. The CEC funds will cover third party testing and validation for durability as well as solar conversion efficiency. “With this new grant funding, Tandem PV will partner with independent labs and technical institutions to rigorously assess its panels’ performance in real-world conditions, including their long-term durability, environmental resilience, and energy yield,” Tandem PV explained.

As for federal energy policy, US President Donald Trump has pulled out all the stops to prevent the US solar industry from growing its footprint in the nation’s power grid, but the seeds of his failure are already in evidence as ratepayers continue to clamor for more kilowatts, more quickly and economically, than any other domestic energy resource can deliver.

Photo: Researchers at Poly U in Hong Kong have presented a roadmap for introducing higher-performing, lower-costing tandem perovskite-silicon solar cells to the market (cropped, courtesy of Poly U via Eurekalert).