Silicon-free tandem photo voltaic cells are a analysis subject for business, tutorial, and institutional labs within the United States. Researchers on the US Department of Energy (DOE) National Renewable Energy Laboratory (NREL) revealed a tandem expertise roadmap within the journal Joule which incorporates rising all-organic, all-perovskite tandem mixtures and cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) units.
Several groups within the United States have introduced lab-scale, all-thin-film cells with conversion efficiencies above 27%. “All-thin-film tandems are a logical place to go ultimately,” mentioned Andries Wantenaar, photo voltaic analyst at market intelligence agency Rethink Research. “Universities have achieved exceptional efficiencies. The first wave was a junction, then the perovskite-silicon tandem after which, lastly, all the skinny movies.
Thin-film benefit
First Solar is the most important mainstream thin-film PV producer. It produces CdTe panels for utility-scale photo voltaic and is investing in rising its annual manufacturing capability to 25 GW by 2026. The firm is investing in R&D centered on cells with increased effectivity and since 2024 introduced a 23.1%-efficient CdTe cell and a 23.6%-efficient CIGS cell, setting data for each applied sciences. CEO Mark Widmar has persistently emphasised the significance of skinny movie to the commercialization of high-efficiency tandem units, a message he reiterated on the commissioning of First Solar’s new analysis middle in Ohio in July 2024.
The Jim Nolan Center is a part of First Solar’s roughly $500 million R&D funding. The 1.3 million sq. toes (120,000 m2) facility contains pilot manufacturing assist for full-size prototypes of thin-film and tandem PV modules.
In May 2024, First Solar was awarded $6 million to develop a perovskite high cell and CIGS backside cell tandem system. The aim is a 27%-efficient design made into “mini modules” with sensible manufacturing processes. The funding was introduced in May 2024 by the DOE’s Solar Energy Technologies Office initiative to advance thin-film photo voltaic manufacturing within the US.
A month earlier, First Solar introduced a partnership with the Center for Solar Energy and Hydrogen Research (ZSW), in Germany, to deal with the efficiency and potential of “the event and optimization of all skinny movie tandem expertise on the gigawatt scale.”
ZSW is thought for its skinny movie fabrication processes for inflexible and versatile substrates. “Our many years of expertise in thin-film photovoltaics match completely for tandems, which at all times have at the least one thin-film cell,” mentioned ZSW researcher Stefan Paetel.
In February 2024, the First Solar European Technology Center and Uppsala University in Sweden achieved the CIGS cell effectivity file of 23.6%. The chief of the Swedish college crew, Marika Edoff, commented on the potential tandem photo voltaic maintain. “For the CIGS expertise, which is thought for its excessive reliability, a world file additionally signifies that it could supply a viable various for brand spanking new purposes in, for instance, tandem photo voltaic cells, ” he mentioned.
In December 2023, First Solar researchers revealed an business overview of all thin-film tandem photo voltaic cells in Journal of Physics: Energy. The researchers concluded that there’s a good likelihood that high-efficiency tandem photo voltaic cells shall be produced in excessive portions “inside the foreseeable future” regardless of the poor system and materials high quality.
New trades
Several US-based startups are engaged on perovskite-silicon tandem units, together with CubicPV, Caelux, Swift Solar, and Tandem PV. The shared view can also be optimistic about the way forward for silicon-free tandems.
“All skinny movie tandems could also be a long-term prospect however there’s nonetheless work to be completed on the underside cell, particularly if it is a perovskite backside cell,” mentioned John Iannelli, founding father of Caelux.
Iannelli mentioned that not like the “big enhancements in stability and effectivity made by wide-bandgap perovskite high cells,” analysis on perovskite for backside cells is “comparatively missing.” Looking forward, Iannelli sees a four-terminal (4T) methodology doubtless for all-perovskite tandems. That’s the identical strategy used within the CaeluxOne product line, an energetic glass answer with perovskite contained in the glass to allow crystal silicon module producers to extend the effectivity of standard-sized panels. For instance, a traditional silicon panel with 21.5% effectivity turns right into a 27% environment friendly tandem system, in line with Iannelli.
At CubicPV, an organization spokesperson mentioned the perovskite-perovskite tandem has potential, “however the improvement time could be very lengthy…
Scott Wharton, the CEO of Tandem PV, expressed the same view. “We undoubtedly suppose {that a} perovskite-perovskite tandem might be on our roadmap,” he commented. “But within the close to time period we’re centered on perovskite-silicon as a extra sensible strategy.”
Swift Solar is at the moment growing high-efficiency perovskite tandem photovoltaics, in line with CEO Joel Jean. “Now, we’re centered on perovskite-silicon tandems however we will additionally see an all-perovskite tandem product sooner or later,” Jean mentioned.
Swift Solar reported making strides within the velocity of skinny movie deposition, which is now 10 occasions sooner than two years in the past. Jean additionally mentioned that the corporate “would not tire of potential wins.”
Perovskite startup Verde Technologies has pursued a silicon-free path from the beginning. Founded in 2021, Verde has developed 22%-efficient single-junction perovskite expertise, which it produces utilizing a roll-to-roll course of. An all-thin-film tandem venture was initiated in Verde’s lab.
“We have a partnership with a business entity that goals for tandems with 30% effectivity by 2027-28,” mentioned Chad Miller, the chief expertise officer of Verde Technologies. “This is the type of step change we anticipate for the PV business.”
Miller added that such an consequence would bypass the traditional silicon PV provide chain “with all its challenges.”
Research and academia
There are a number of US college analysis groups investigating tandem photo voltaic units with out silicon. For instance, on the Wright Center for Photovoltaics Innovation and Commercialization (PVIC), on the University of Toledo, researchers demonstrated a 4T tandem made utilizing an in-house cadmium selenium telluride backside cell and a steel halide perovskite high cell and again contact design, which gives 25% effectivity. The identical group additionally demonstrated an all-perovskite tandem photo voltaic cell with 27.8% effectivity.
“Tandem analysis is an space of rising significance and curiosity inside the scientific group,” defined PVIC chief Zhaoning Song. “Many researchers and firms are searching for options to unlock the potential of tandem photo voltaic cells. Tandem skinny movies maintain nice promise for future purposes but additionally require additional analysis and improvement to understand their full potential.
At Northwestern University, inside the Sargent Group within the Department of Chemistry, latest collaborations have resulted in lab-sized, all-thin-film units with improved stability and energy conversion efficiencies that as much as 28.1%. “In addition to all-perovskite double junctions, triple-junction photo voltaic cells have nice potential for increased efficiencies,” mentioned assistant professor Bin Chen.
“To get there, we have to develop wider bandgap supplies. The excellent news is that lots of the methods we use for double junctions will also be used for triple junctions so we anticipate to see vital enhancements in triple-junction efficiencies within the subsequent few years.
Looking forward
Commercialization of all-thin-film tandem and multijunction expertise will allow higher form-factor flexibility, amongst different advantages. A higher variety of kind components and module specs also can open up new purposes for photo voltaic. The skill to generate higher energy per unit space, because of high-efficiency thin-film units, additionally makes PV sensible for a lot of extra purposes, accelerating photo voltaic adoption. “What is required for the subsequent 5 terawatts of PV adoption just isn’t the identical as what is required for the primary 5,” mentioned Joseph Berry, NREL researcher and roadmap co-author.
Meanwhile, bettering the power and lifetime of the module are the principle analysis areas. If perovskites are for use, there shall be a necessity for brand spanking new fashions for predicting power output and for brand spanking new methods for measuring module efficiency, in line with Timothy Silverman, who leads NREL’s perovskite module subject testing. since 2022 within the DOE-funded PV accelerator for commercializing applied sciences.
Similar qualification issues needed to be overcome beforehand with different thin-film applied sciences, in line with Silverman. “That’s why it is necessary to start out finding out it now,” he added.
To overcome the challenges for tandem expertise associated to the complexity of integrating sub-cells, thermalization points, and the necessity for environment friendly deposition expertise and different challenges, it’s doubtless that the consortia of business and analysis organizations will drive progress within the coming years, in line with Emily Warren, NREL researcher and co-author of the roadmap. “As a nationwide lab, analysis on this expertise have to be completed now to make it a risk in 5 – 6 years,” he mentioned.
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