New Pathway Emerges To Improve Polycrystalline Thin-Film Solar Cell Performance
Puzzling out and testing new ways to improve the efficiency of cadmium telluride (CdTe) polycrystalline thin-film photovoltaic materials is a typical day in the life of National Renewable Energy Laboratory (NREL) research scientists Matthew Reese and Craig Perkins. Like any good puzzlers, they bring curiosity and keen observation to the task. These skills led them, over time, to make an intriguing observation. In fact, their discovery may prove to be a boon for the next generation of several different types of thin-film solar cells.
When fragments of solar cell material are crystallized together, or “grown” — think of a piece of rock candy growing in layers in a cup of sugar — they create a polycrystalline solar cell. With many layers come many surfaces, where one layer ends and another begins. These surfaces can cause defects that restrict the freedom of electrons to move, reducing the cell’s efficiency. As the cells are grown, researchers can introduce specific compounds that minimize the loss of electrons at these defects, in a process called “passivation.”
Reese, Perkins, and Colorado School of Mines doctoral student Deborah McGott noticed that the three-dimensional (3D) CdTe solar cells’ surfaces appeared to be covered in a very thin, two-dimensional (2D) layer that naturally eliminated surface defects. This 2D passivation layer forms in sheets on the 3D light-absorbing layer as the cell is growing, in a standard processing technique that is used around the globe. Despite the ubiquity of this 2D passivation layer, it had not been observed or reported in the research literature. Reese, Perkins, and McGott believed 2D passivation was also occurring naturally in other thin-film solar cells, like copper indium gallium selenide (CIGS) and perovskite solar cells (PSCs). They realized that this observation could lead to the development of new methods to improve the performance of many types of polycrystalline thin-film cells.
To confirm their hypothesis, they discussed it with NREL colleagues in the CdTe, CIGS, and PSC research groups. Through many informal discussions involving coffee, hallway chats, and impromptu meetings, Reese, Perkins, and McGott arrived at an “aha” moment. Their CdTe and CIGS colleagues confirmed that, while their research communities were not generally trying to perform 2D surface passivation in the 3D light-absorbing layer, it was, in fact, occurring. The PSC researchers said that they had noticed a 3D/2D passivation effect and were beginning to intentionally include compounds in device processing to improve performance. The “aha” moment took on even more significance.
“One of the unique things about NREL is that we have large groups of experts with different pools of knowledge working on CdTe, CIGS, and PSC technologies,” Reese said. “And we talk to each other! Confirming our hypothesis about naturally occurring 3D/2D passivation with our colleagues was easy because we share the successes and setbacks of our diverse research in an ongoing, informal, and collaborative way. We learn from each other. It is not something that typically happens in academic or for-profit-based polycrystalline thin-film solar cell research, where information is closely held, and researchers tend to remain siloed in their specific technology.”
The details of Reese, Perkins, and McGott’s discovery are presented in the article “3D/2D passivation as a secret to success for polycrystalline thin-film solar cells,” published in the journal Joule.
Supporting Evidence in the Literature
To confirm their findings, McGott conducted an extensive literature search and found considerable supporting evidence. The literature confirmed the presence of passivating 2D compounds in each of the CdTe, CIGS, and PSC technologies. No mention was made, however, of the 2D compounds’ ability to improve device performance in CdTe and CIGS technologies. While many articles on PSC technologies noted the naturally occurring 3D/2D passivation effect and discussed efforts to intentionally include specific compounds in device processing, none suggested that this effect might be active in other polycrystalline thin-film photovoltaic technologies.
Polycrystalline thin-film solar cells are made by depositing thin layers, or a thin film, of photovoltaic material on a backing of glass, plastic, or metal. Thin-film solar cells are inexpensive, and many people are familiar with their more unique applications. They can be mounted on curved surfaces — to power consumer goods, for example — or laminated on window glass to produce electricity while letting light through. The largest market for thin-film solar cell applications, however, is for CdTe thin film on rigid glass to make solar modules. CdTe modules are deployed at utility scale, where they compete directly with conventional silicon solar modules. Currently, commercial thin-film modules are generally less efficient than the best single crystal silicon solar modules, making performance improvements a high priority for polycrystalline thin-film researchers.
Key Properties of 2D Materials
Reese, Perkins, and McGott’s team used surface science techniques combined with crystal growth experiments to show that the 2D layers existed at and passivated 3D absorber surfaces in the three leading polycrystalline thin-film photovoltaic technologies. They then analyzed the key properties of successful 2D materials and developed a set of principles for selecting passivating compounds.
Finally, the team outlined key design strategies that will allow 3D/2D passivation to be employed in polycrystalline thin-film photovoltaic technologies more generally. This is particularly important because each 3D material requires a specific passivation approach.
The literature results, combined with lab-based observations, show that 3D/2D passivation may be the secret to success in enabling next-generation thin-film solar cells, particularly if researchers freely share the knowledge developed for each technology. The lack of 3D/2D passivation may even shed light on the stalled performance improvements of some polycrystalline technologies such gallium arsenide. By drawing parallels between the three technologies, Reese, Perkins, and McGott hope to demonstrate how the knowledge developed in each can — and should — be leveraged by other technologies, an approach that is seldom seen in polycrystalline thin-film solar cell research.
CdTe, CIGS, and PSC thin-film research at NREL is funded by the Department of Energy’s Solar Energy Technologies Office. Additional funding for Reese and McGott’s research is provided by the Department of Defense’s Office of Naval Research.
Learn more about photovoltaic research at NREL.
Article courtesy of the NREL, The U.S. Department of Energy.
Robotaxi network Waymo is continuing the rapid expansion of its test fleet vehicles in new cities around the US as it looks to offer more driverless ride options to the public. The Alphabet Inc. subsidiary announced three new cities where test vehicles will roll out en route to commercial services, marking Waymo’s second expansion announcement in just three days.
As we recently pointed out, 2025 continues to be a pivotal year for autonomous rideshare developer Waymo, as it expands its fleet of test vehicles and public robotaxis to new cities around the US. This week, in particular, has been quite newsworthy, as Waymo has been announcing expansions to new cities around the US.
Today, Waymo’s robotaxi vehicles offer public rides in Atlanta, Austin, Los Angeles, Phoenix, and San Francisco – three of those cities recently gained freeway access. Two days ago, Waymo confirmed the expansion to five additional cities: Miami, Dallas, Houston, San Antonio, and Orlando.
This new confirmed previous reports from Waymo that cities like Miami were in the works. Washington, DC, Nashville, and London have also been previously announced. Today, Waymo confirmed expansion to three more cities, with test vehicles rolling out in those regions immediately.
Waymo to quadruple the cities its vehicles are available
Waymo posted three “new city alerts” on its website this morning, confirming plans to roll out robotaxi vehicles in Minneapolis, Minnesota, New Orleans, Louisiana, and Tampa, Florida. As it has with all the cities mentioned above, Waymo is laying the initial groundwork in new areas, such as NOLA, to “integrate seamlessly with the community and alongside existing transportation options.”
The recently announced rollout will follow the same phased approach used to achieve public robotaxi rides in the five cities where Waymo currently operates, beginning with manual drivers in its test fleet. Those Waymo vehicles currently consist of Jaguar I-Pace SUVs and the Zeekr RT – a purpose-built EV for the company.
According to the company, those test vehicles can be spotted on new city streets immediately, especially ahead of winter in Minneapolis, for example, so that the Waymo team can test its technology in snow conditions. Here’s a breakdown of Waymo’s current and pending robotaxi network:
- Waymo Cities With Public Robotaxi Operations:
- Atlanta
- Austin
- Los Angeles
- Phoenix
- San Francisco
- Cities With Plans For Future Waymo Operations:
- Dallas
- Denver
- Detroit
- Houston
- Las Vegas
- London
- Miami
- Minneapolis
- Nashville
- New Orleans
- Orlando
- San Antonio
- San Diego
- Seattle
- Tampa
- Tokyo
- Washington, DC
According to Waymo, more cities will be announced as the company intends to more than quadruple the number of cities where its robotaxi vehicles are available to the public.
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Environment
Kia’s first electric van snags a historic win, claiming 2026 International Van of the Year
The PV5, Kia’s first 100% electric van, was unanimously chosen as the 2026 International Van of the Year, becoming the first Korean model to win the prestigious award.
The Kia PV5 wins International Van of the Year
Kia’s electric van continues to impress. After its debut earlier this year, the PV5 was named International Van of the Year at SOLUTRANS 2025 in Lyon, France.
The PV5 beat out six other finalists and was unanimously selected by 26 leading commercial journalists for the most authoritative global award in the light commercial vehicle (LCV) segment.
To have the PV5 named International Van of the Year is “an exceptional honor,” Kia’s CEO Ho Sung Song said after winning the award.
The accomplishment is not only a testament to the potential of fully electric vehicles in the commercial space, but also Kia’s belief that it can “redefine the segment,” according to Song.
Kia’s electric van is now the first Korean vehicle, and Asia’s first electric van, to win the award. The PV5 is Kia’s first fully electric van as part of its new Platform Beyond Vehicle (PBV) business.
Earlier this week, Kia introduced a new Chassis Cab variant at SOLUTRANS 2025, adding to the Passenger 5-seater and Cargo Long models that are rolling out across Europe and South Korea. Starting in 2026, Kia plans to launch the Chassis Cab, Cargo Standard (L1H1), and High Roof (L2H2) variants. However, that’s just the start.
Kia revealed seven different PV5 body types during a tech day event in July, including a light camper, a refrigerated truck, a luxury “Prime” passenger, an open-bed version, and several others.
In 2027, Kia will expand with a larger PV7 van, followed by an even bigger PV9. All electric vans are based on the modular E-GMP.S platform, which enables different variants.
The PV5 Cargo Long Range set a new Guinness World Record for the “greatest distance travelled by a light-duty battery-powered electric van with maximum payload on a single charge” in September.
Powered by a 71.2 kWh battery with 665 kg (1,466 lbs) payload, the PV5 drove 693.38 km (430.84 miles) without stopping to charge.
All electric vans are built at Kia’s dedicated Hwaseong EVO plant in South Korea. Last week, the company marked a milestone after opening the first PV5 production hub at the site. Once complete, the hub will be about the size of 42 soccer fields with an annual production capacity of 250,000 units.
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Pedego, one of the most recognizable names from the early days of American e-bike brands, is entering a new era. The company has been acquired by the “US-based” ownership group behind the Asian e-bike brand Urtopia, a relatively young, tech-forward electric bike brand known for carbon fiber e-bikes with built-in connectivity and smart features. The result is a newly formed New Pedego Holdings Inc., which both companies are pitching not as a takeover, but as a reboot designed to modernize Pedego and rebuild the dealer network that once made it a retail powerhouse.
The new entity will be led by Pedego CEO Larry Pizzi, an industry veteran and longtime advocate for e-bike legislation. Pizzi says the partnership grew out of something very simple: Pedego dealers were already selling Urtopia bikes – and the company claims they were selling well. As he told BRAIN, “Fifty-eight dealers took on Urtopia and it was like magic,” noting that the sleeker, more futuristic Urtopia models pulled in a distinctly younger audience than Pedego’s traditional comfort-cruiser demographic that has long been popular with the more silver-haired crowd.
That complementary fit paved the way for a broader deal. Verlinvest, the Belgian investment group that bought Pedego in 2021, had already signaled its desire to exit earlier this year.
Pizzi spent months searching for a buyer before selecting Urtopia’s backers, calling the partnership a way to combine Pedego’s community-focused retail model with Urtopia’s engineering and manufacturing strengths.
According to the official announcement, Pedego gains access to Urtopia’s supply chain, lean manufacturing processes, and smart-bike technology – all of which the company says will significantly reduce production costs and bring a wave of new, lighter, more connected models starting in Spring 2026. The two brands will continue to operate distinctly, with Pedego stores selling Pedego bikes, Urtopia bikes, and a small number of approved third-party brands. Urtopia will keep selling online and through independent retailers in the US and Europe.
But one of the biggest storylines is dealer expansion. Pedego peaked at around 220 dedicated stores during the pandemic before shrinking to around 120 today. New Pedego Holdings plans to rebuild aggressively, forecasting a return to growth in 2026 with a goal of more than 500 US and Canadian retail locations within three years – a massive ramp-up that would reestablish Pedego as the largest dedicated e-bike retail network in North America.
Pedego hasn’t launched a new model in over a year and a half, but that drought is expected to end next year. If the Urtopia partnership delivers the innovation and efficiency the company promises, Pedego could be gearing up for one of the biggest comebacks in the e-bike industry. If not, this could be another Hail Mary to cap off a year of stunning falls from grace.
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