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Qcells says it plans to open a gigawatt-scale factory for perovskite-silicon tandem solar panels in 2029 and is testing full-size panels in the field. The technology has posted high laboratory efficiency results, but long-term durability and commercial performance remain unresolved.
Qcells plans to open a gigawatt-scale factory for perovskite-silicon tandem solar panels in 2029, the company’s global chief technology officer, Danielle Merfeld, told Canary Media. The plan would put the U.S.-active manufacturer among companies seeking to move tandem panels from research and pilot production into commercial-scale manufacturing, although long-term product durability has yet to be established.
Qcells is testing full-size tandem panels in the field, according to Merfeld. The company has worked on tandem cells since 2016, opened a research-and-development pilot line in Germany in 2022, and began operating a 40-megawatt pilot line in South Korea in 2024. That line produces full-size panels, while some competing developers are still moving from small test cells to larger products, the report said.
In 2024, an independent body confirmed a 28.6% efficiency result for a standard-size silicon cell layered with perovskites, setting a tandem record at the time, according to the source report. Qcells also said in July that its tandem panel passed testing against quality standards set by UL and the International Electrotechnical Commission. Those tests subject panels to accelerated physical stresses; they do not establish that a product will last for decades in everyday operating conditions.
Merfeld did not disclose the perovskite materials Qcells is using or provide degradation data from its field tests. The company’s factory plan is therefore a stated target, not evidence that the panels are already being manufactured at gigawatt scale or that their commercial performance has been proven.
More Power From Each Panel
Tandem panels layer a perovskite material over conventional silicon to capture sunlight in ways a single silicon cell cannot. If manufacturers can make panels that remain reliable and cost-effective, they could produce more electricity from the same panel area. That could increase the output of existing rooftops and solar sites, or allow a project to generate a given amount of power on less land.
Higher output per area may also reduce some project costs that are not tied directly to the panels, including land, wiring, supporting equipment and labor. Those benefits depend on the technology reaching commercial scale at a competitive price and performing reliably over time. The factory proposal matters because it signals that Qcells is aiming to tackle those manufacturing challenges, not just pursue laboratory efficiency records.
The outcome could affect solar developers, manufacturers and project financiers. Banks typically need confidence that equipment will keep producing power over a long operating life before they finance installations. Durability evidence will be as important as efficiency in determining whether tandem panels can become a bankable product.
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From Lab Records to Factory Plans
Conventional high-performance panels convert sunlight to electricity at around 24% efficiency, according to the report. Merfeld said conventional panel efficiency has risen by about half a percentage point per year over the past decade. Qcells’ reported 28.6% tandem result suggests a sizable laboratory gain, but the report notes that conventional panels may improve before the proposed 2029 production start.
Qcells is not the only company pursuing large-scale production. China’s GCL said it opened a 1-gigawatt factory in Kunshan last year. In the United States, Tandem PV CEO Scott Wharton told Canary Media that his company is targeting 2028 to build a gigawatt-scale factory. Other developers named in the report include Oxford PV and Caelux.
Factory capacity alone does not settle whether tandem solar is commercially ready. The report says public support available to manufacturers in China differs from what companies elsewhere can access, limiting how easily the GCL project can be used to judge the technology’s commercial prospects in other markets. Qcells’ manufacturing experience and pilot lines provide a route toward scale, but the panels still need to establish reliability in operation.
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Durability Still Needs Proof
It is not yet clear whether Qcells’ panels will sustain commercial performance over the decades expected of solar equipment. No tandem panel has operated for more than 20 years, according to the report, so accelerated testing provides an indication of resilience rather than a record of long-term field performance. Qcells has not shared its field-test degradation data or the perovskite formulation it selected.
The report also does not provide the proposed factory’s location, investment cost, expected construction schedule beyond the 2029 target, or planned output details beyond gigawatt scale. It remains unclear whether Qcells will meet that timetable, what the panels will cost, and how their efficiency and reliability will compare with conventional products available by then.
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Field Tests and Factory Milestones
Qcells says it has installed tandem panels at its own test sites over the past year. Continued field operation can provide evidence about how the panels respond to real-world sunlight and weather, though a short test period cannot establish decades of service life. The company’s next public milestones would include sharing additional performance and degradation results and providing more detail about the proposed factory.
The 2029 target will also be measured against competing plans, including Tandem PV’s stated 2028 factory goal. Whether any developer can move from pilot production to sustained commercial output will depend on manufacturing progress, product reliability and financing. For now, Qcells has announced an ambition and reported testing milestones; the scale-up and long-term commercial case remain ahead.
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Key Questions
What does Qcells plan to build?
Qcells plans a gigawatt-scale factory for perovskite-silicon tandem solar panels, with production targeted for 2029. The company has not provided further factory details in the reported information.
What are tandem solar panels?
They combine conventional silicon cells with perovskite layers. The pairing can capture sunlight more efficiently than silicon alone, but manufacturers still have to establish durability and commercial performance.
Has Qcells proved the panels will last for decades?
No. Qcells reported passing accelerated quality tests and said it has panels in field testing, but decades of operating history are not available for tandem panels. The company has not released field-test degradation data.
How does Qcells’ plan compare with other companies’ projects?
China’s GCL said it opened a 1-gigawatt factory last year, while Tandem PV has said it is targeting a gigawatt-scale factory in 2028. These plans do not by themselves prove that tandem panels have achieved broad commercial readiness.
Why could tandem panels matter to solar projects?
If they prove reliable and cost-effective, tandem panels could generate more electricity in the same area, or meet a project’s output target using less space. Any savings would depend on panel cost, operating life and installation requirements.
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