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.
Burlingame, California-based Peak Energy just scored a huge win for sodium-ion batteries. The company announced a multi-year deal with utility-scale battery storage developer Jupiter Power to supply up to 4.75 GWh of sodium-ion battery systems between 2027 and 2030.
Under the agreement, Peak will deliver 720 MWh of storage in 2027 – the largest single sodium-ion battery deployment announced so far. The deal also includes an option for an additional 4 GWh of capacity through 2030, bringing the total contract value to more than $500 million.
Sodium-ion vs. lithium-ion
Peak Energy says its sodium-ion batteries degrade less over time and have lower operations and maintenance costs than lithium-ion systems. Because the batteries don’t degrade as quickly, operators don’t need to add more capacity later in a project’s life to maintain performance. They also use a fully passive cooling system that eliminates pumps, fans, and other components used in lithium-ion setups, reducing maintenance and safety risks.
The company claims its grid-scale sodium-ion system uses up to 97% less auxiliary power, offers about 30% better cell degradation performance over 20 years, and comes with a lower total cost of ownership.
Why this deal matters
The agreement marks a significant step forward for the emerging sodium-ion sector, which has been gaining momentum as a safer and lower-cost alternative to lithium-ion for long-duration and grid-scale energy storage. It also underscores the growing effort to build a domestic sodium-ion battery supply chain in the US.
“From day one, we’ve believed sodium-ion will be the winning technology for grid-scale storage, which is essential to meet rising demand from hyperscalers and AI,” said Landon Mossburg, Peak Energy’s CEO and cofounder. “Deploying the world’s largest sodium-ion energy storage system with one of the nation’s top independent power producers proves that sodium is ready for today and will dominate the future.”
Mike Geier, CTO at Jupiter Power, said the company is “excited to support domestic battery energy storage manufacturing as we continue to increase the deployment of firm, dispatchable energy when and where it’s most needed,” and called Peak’s approach to sodium-ion “a potential game changer for the industry.”
Read more: The US’s first grid-scale sodium-ion battery is now online
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![The new 2026 Lexus ES is an upgrade in just about every way [Video]](https://i0.wp.com/electrek.co/wp-content/uploads/sites/3/2025/11/new-2026-Lexus-ES-EV.jpeg?resize=1200,628&quality=82&strip=all&ssl=1)
Lexus claims the new ES “takes sedan styling, luxury, and refinement to a higher level” with a complete redesign. With the 2026 ES arriving soon, Lexus offered a closer look at the upgrades inside and out.
The new 2026 Lexus ES debuts in EV and hybrid forms
The eighth-gen ES is bringing more than a sharp new style. Lexus overhauled its flagship sedan from the ground up for the 2026 model year, which will include battery electric (BEV) and hybrid (HEV) powertrain options.
Inspired by the radical LF-ZC show car, the 2026 ES has been fully redesigned with what Lexus calls the “Experience Elegance and Electrified Sedan” concept, aimed at further refining the driving experience.
The new design centers on a redesigned “spindle body” that extends from the hood to the bumper. It also features a redesigned grille, replacing the signature Lexus spindle grille as the brand looks for a new identity in the electric era.
Inside, the new 2026 ES features the latest version of the Lexus Interface multimedia system. The setup includes a 14″ touchscreen with wireless Apple CarPlay and Android Auto, and a 12.3″ driver display cluster.
Based on the redesigned TNGA GA-K platform, the new ES will be available in battery electric (BEV) and hybrid (HEV) powertrains for the first time.
The 2026 Lexus ES lineup consists of two models: the ES 350e, a front-wheel-drive (FWD) model, and the ES 500e, an all-wheel-drive (AWD) model.
Lexus expects the ES 350e to have a driving range of 300 miles when fitted with 19″ wheels, while the ES 500e has an estimated driving range of 250 miles.
Both the ES 350e and 500e feature a built-in NACS port to recharge at Tesla Superchargers. Using DC fast charging, it can recharge from 10% to 80% in about 30 minutes under “ideal conditions,” according to Lexus.
With its debut just around the corner, Lexus offered a closer look at the new 2026 ES inside and out in a new video.
Lexus has yet to announce prices, but the redesigned ES is expected to start at about $45,000 to $50,000, or slightly more than the outgoing model.
After launching the upgraded RZ earlier this month, Lexus said the ES would be next. It’s expected to go on sale in Spring 2026.
What do you think of the redesigned 2026 ES? Do you like the new Lexus design? Let us know your thoughts in the comments below.
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Tesla has launched a new version of the Model Y in China, and it’s achieving an impressive new range rating – thanks to a new battery cell from South Korea’s LG.
The new variant, a five-seat, rear-wheel drive long-range model, has been released with an 821-km range based on China’s CLTC standard.
While the CLTC rating is known to be optimistic, 821 km (about 510 miles) is an impressive number and the longest range Tesla has offered in its Model Y lineup to date, which is going to help it be more competitive in the Chinese market.
This new extended range Model Y version is made possible by using the 78.4-kWh ternary lithium-ion battery pack from LG Energy Solution, the same pack found in the also recently launched 830-km range Model 3 variant.
The new long-range RWD Model Y starts at RMB 288,500, which translates to just over $40,500 USD.
The launch comes at a critical time for Tesla in China, which has seen its sales slump in recent months. The automaker recorded its lowest monthly sales in October since November 2022, falling out of the top 10 list for new energy vehicle (NEV) sales.
That’s despite a continued surge in electric vehicle sales in China. Tesla is not benefiting from it amid strong competition.
According to local Chinese media reports, the new 821-km Model Y is already gaining traction with some anecdotal reports of enthusiasm at Tesla stores.
The reports are partly supported by Tesla quickly extending delivery timelines from 2-4 weeks to 4-6 weeks just hours after launch.
Electrek’s Take
I think this is going to be suitable for a decent short-term bump in demand, but it’s still on the expensive side for the Chinese market.
For example, now the Model Y beats the Xpeng G6’s max range of 755 km, but the G6 with this range costs 234,900 RMB (approximately $32,900 USD), which is significantly cheaper.
Every 10,000 RMB tranche lower means a lot more demand in China.
Tesla needs to launch its new “standard” versions to start making a difference with demand long term in China.
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