Next-Gen Thermoelectrics Unlock 15x Boost in Solar Output

As renewable energy comes from natural resources and is replenished, it can help reduce our reliance on fossil fuels, address climate change, and meet our need for a sustainable energy future.

These abundant, naturally replenished energy sources with minimal emissions include sunlight, wind, water, biomass, and geothermal heat.

Among these, solar energy is the primary source of renewable energy. With the sun as an infinite source of power, solar energy is inexhaustible, making it the most abundant renewable energy source available.

In 2024, global solar power reached a record high, with installations exceeding 600 GW, a 33% increase from the previous year, accounting for 81% of all new renewable energy capacity worldwide. As a result, solar power accounted for about 7% of the global electricity supply, nearly doubling its share of the electricity mix in just three years.

The International Energy Agency (IEA) actually expects solar photovoltaics (PV) to become the largest renewable energy source by 2029, benefiting from supportive regulatory policies and the strong decline in the cost of electricity generated from solar panels. 

A PV cell or a solar cell is a device that converts sunlight directly into electric power. Some cells can even convert artificial light into electricity. However, they aren’t issue-free. One of the primary limitations of a PV cell is its temperature, which significantly impacts its conversion efficiency.

This is where another widely used technology, solar thermoelectric (TE), comes into the picture. 

Going Beyond Solar PVs to Solar Thermoelectric Generators (STEGs)

A thermoelectric generator (TEG) can address the challenge of conversion efficiency in PV cells by converting wasted heat into electrical energy.

TEGs are known for their high reliability, long lifetime, and absence of mechanical moving parts, making them a viable and promising option for integration with PV cells in high-temperature applications.

Also called a Seebeck generator, a thermoelectric generator (TEG) is a device that converts heat directly into electricity through the Seebeck effect.

In this effect, a temperature difference between two dissimilar conductors or semiconductors generates voltage, caused by the movement of charge carriers. 

When heat is applied to one of the conductors or semiconductors, electrons move towards the colder end, creating a potential difference. If connected through a circuit, the direct current flows through it.

So, based on the Seebeck effect, TE materials generate a voltage when subjected to a temperature difference across their ends. When positioned between a solar absorber and a heat dissipator in order to establish a temperature difference and generate power, they are referred to as solar thermoelectric generators (STEGs).

The thermal-to-electrical conversion efficiency of these STEGs is determined by the TE material’s dimensionless figure of merit (ZT) and the temperature difference between the hot side and the cold side across the device. 

As a result, solar absorbers of STEGs have a much wider absorption band, allowing the photon energy of the entire solar spectrum to be utilized, unlike solar PVs that can use only a narrow band of sunlight near the semiconductor bandgap. However, their thermoelectric efficiency is very low.

As the latest research noted, the ZT value of TE material still remains around one, even after decades of extensive research. ZT is a key metric for evaluating the performance of thermoelectric materials, with a higher ZT value indicating a more efficient thermoelectric material for generating electricity from a given temperature difference.

The lack of high-efficiency thermoelectric (TE) materials and compact heat sinks for heat dissipation is what limits the commercial adoption of STEGs.

To address these very issues, a team of researchers has developed a strategy that can enhance the power generation of STEG by 15 times while increasing the weight by only 25%.

STEG Efficiency Challenges: The Need for Better Absorbers & Heat Dissipators

Global energy needs are rapidly increasing, driven by population and economic growth. 

According to IEA, the global demand for electricity increased by 4.3% in 2024, a big jump from the 2.3% increase in 2023.

So, going forward, the world will need an ever-increasing supply of energy, but more importantly, clean energy in order to combat climate change, reduce greenhouse gas (GHG) emissions, and achieve energy independence.

In this quest for sustainable clean energy, researchers have turned to solar thermoelectric generators (STEGs) as a promising source of solar electricity generation, since they can harness not only sunlight but also other forms of thermal energy.

Currently, however, most STEGs convert less than 1% of sunlight into electricity, whereas residential solar panel systems are capable of 15% to 20% conversion efficiency. 

So, to really take advantage of these devices, we must first overcome their efficiency limitations. 

What we need is to come up with new ways to enhance STEG power generation. Solar thermoelectric generators produce more power at higher temperature differences, and that can be achieved by maximizing solar energy absorption and minimizing heat loss on the hot side while efficiently dissipating heat on the cold side.

Moreover, STEGs could prove valuable in powering wearable electronics, medical sensors, wireless sensor networks, and avionic devices.

However, these high-power-density applications require lightweight selective solar absorbers (SSAs) for the hot side and heat dissipators for the cold side. In order to harness the maximum amount of solar energy, the absorber (SSA) must exhibit high optical absorption in the solar spectral range (300–2500 nm) while maintaining low emissivity in the IR (2.5–20 μm) to minimize radiation loss. 

The optical performance of absorbers can be optimized through structural design and material selection.

This includes plasmonic absorbers, double ceramic layer absorbers, multilayer film absorbers, and photonic crystal absorbers. However, despite all these advances, most absorbers require complex equipment and time-consuming fabrication processes, which restrict their scaling at an affordable cost. 

Additionally, increasing the output power of STEG often requires bulky and complex cooling systems to lower the cold side temperature and increase the temperature difference, presenting yet another challenge.

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Black Metal Tech and Femtosecond Lasers: A Game-Changing Strategy

To overcome STEG problems, the researchers from the University of Rochester’s Institute of Optics have developed a spectral engineering and thermal management strategy that reduced weight and increased power production.

New techniques for creating this more powerful STEG device are detailed in a study¹ published in Light: Science and Applications.

“For decades, the research community has been focusing on improving the semiconductor materials used in STEGs and has made modest gains in overall efficiency.”

– Chunlei Guo, a professor of optics and physics and a senior scientist at Rochester’s Laboratory for Laser Energetics.

He added:

“In this study, we don’t even touch the semiconductor materials—instead, we focused on the hot and the cold sides of the device. By combining better solar energy absorption and heat trapping at the hot side with better heat dissipation at the cold side, we made an astonishing improvement in efficiency.”

The key here was the special black metal technology. Back in 2020, the same team showed that by using a femtosecond (fs) laser, which helped them create unsinkable metallic structures² a few months prior to that, they could also develop highly efficient solar power generators³.

At that time, they turned the shiny, highly reflective surface of a metal pitch black, calling it black metal technology. With femtosecond laser pulses, they can turn almost any metal pitch black.

The team experimented with copper, steel, aluminum, and tungsten. After treatment with nanoscale structures, they found tungsten to have the highest solar absorption efficiency. They were able to enhance the efficiency of thermoelectric production by 130% compared to untreated tungsten, which is commonly used as a thermal solar absorber.

So, building on that, this time, the researchers transformed a regular tungsten (W) on the hot side into an absorber (W-SSA) through the fs-laser processing technique.

The tungsten was transformed into ‘black metal’ by turning its surface pitch-black, which made it highly efficient at selectively absorbing light at the solar wavelengths while reducing heat dissipation at other wavelengths.

This was achieved through ultra-fast and precision etching, using the powerful fs laser pulses, which created nanoscale structures on the metal’s surface. So, instead of modifying the semiconductor materials themselves, the team improved how the hot side absorbs sunlight and retains heat.

A greenhouse chamber for tungsten selective solar absorbers (W-SSA) has also been created to reduce convective loss.

To create a mini greenhouse, like on a farm, the black metal was covered with a piece of plastic. “You can minimize the convection and conduction to trap more heat, increasing the temperature on the hot side,” said Guo. The team was able to minimize the heat loss by over 40%.

Meanwhile, on the cold side, the same laser technique was used to transform a regular aluminum (Al) into a mega-capacity heat dissipator with tiny structures. This created a heat sink to improve the dissipation of heat through radiation as well as convection. 

The cooling performance of the treated aluminium was double that of a regular Al heat dissipator.

In all of this, as we saw, the fs-laser processing technique played a key role. Notably, this technique requires just one step and is scalable. This simple subtractive technique can also be applied to a range of materials with complex geometry, such as polymer, glass, dielectrics, semiconductors, and metals.

Being a purely physical approach, it is also more environmentally friendly than other methods. 

The femtosecond (one quadrillionth of a second) laser produced a range of microstructures on aluminum and nanostructures on tungsten.

Then, optimizing the size and density of these structures enabled the researchers to boost solar absorption of W while minimizing its IR emissivity at the hot side. They obtained greater than 80% absorption efficiency at elevated temperatures.

On the cold side, they increased IR emissivity across the complete blackbody radiation spectrum for aluminum and its surface area for heat dissipation. Doing so greatly enhanced solar-to-thermal conversion efficiency.

The team demonstrated how their solar thermoelectric generator (STEG) can be used to power LEDs far more effectively than existing methods.

The tech, Gao noted, could also be used to power microelectronic devices like wearables, smart devices, and autonomous sensors for the Internet of Things (IoT). Moreover, it can serve as an off-grid renewable energy system in remote and rural areas.

As the study noted, STEGs can also be used in conjunction with advanced solar energy devices, such as spectral splitting hybrid PV-TE systems and low-cost dye-sensitized solar cells (DSC), which can generate power under low-light conditions, thereby improving the energy output for power-demanding applications.

Investing in Solar Energy

In the renewable energy space, Nextracker Inc. (NXT ) stands out for being a high-growth company.

With a market cap of $10 billion, NXT shares are currently trading at $67.59, up 85% this year so far. Just last week, the company’s shares hit a new high at around $69. With that, its EPS (TTM) is 3.67, and the P/E (TTM) is 18.42. There’s no dividend yield to earn, though.

Nextracker Inc. (NXT )

Nextracker is a solar technology platform provider that offers electrical solutions, integrated trackers, and yield optimization and control systems. The company’s advanced technology allows solar power plants to follow the movement of the sun across the sky and optimize performance. 

Its products and services include NX Foundation, NX Horizon, NX Navigator, NX Global, PowerworX, TrueCapture, and Services Electrical Balance of System (eBOS).

This month, Nextracker released its sustainability report, in which it noted attaining a Total Recordable Incident Rate (TRIR) of 0.61, surpassing the US safety operations goal of 1.2.

Nextracker introduced NX Foundation Solutions for improving solar deployment across all soil types. NX Horizon low-carbon tracker (LCT) systems have also been released to reduce carbon emissions (tracker-related) by as much as 35%.

In regard to GHG emissions and resource efficiency, the company committed to setting targets in line with the globally recognized framework (SBTi), published its first Task Force Climate Financial Disclosure (TCFD) index, obtained a third-party assurance for its Scope 1 and Scope 2 GHG emissions data, and earned ISO 14001:2015 certification for Environmental Management System in the US.

ISO 9001 certification was also achieved for quality management across operations in the US, India, and Brazil. 

Amidst this, Nextracker was recently selected by one of the largest renewable energy companies in the South American nation. Casa dos Ventos selected it to provide 1.5 GW of its solar tracker systems for their four new projects in Brazil. These include solar and solar-and-wind hybrid projects.

“Securing a multi-project commitment from a renewable energy leader like Casa dos Ventos reflects the growing importance of trusted partnerships when it comes to performance and long-term reliability in today’s solar industry.”

– Alejo Lopez, vice president, Nextracker Latin America

Nextracker has also collaborated with UC Berkeley to establish a new research center (the CAL-NEXT Center for Solar Energy Research) to advance solar power plant technology to support future energy needs. The company made a $6.5 million contribution to the initiative.

As for the company’s financials, late last month, it reported the first quarter of fiscal year 2026, which ended June 27, 2025. In this period, it recorded $864 million in revenue, up 20% YoY.

GAAP gross profit increased 19% YoY to $282 million, while GAAP operating income jumped 16% YoY to $186 million. Adjusted gross profit was up 18% to $285 million, and adjusted EBITDA was up 23% to $215 million. Nextracker’s total backlog for this period was over $4.75 billion.

It also reported operating cash flow of $81 million and $743 million of cash at the end of the quarter, with no debt. During this quarter, the company invested $86.8 million in strategic acquisitions to support new growth initiatives.

“Nextracker delivered another strong quarter across all key financial metrics and saw continued market share momentum.”

– Founder and CEO Dan Shugar

Just last month, Nextracker announced the launch of its AI and robotics business initiative. “Scaling solar to meet global energy demand requires a new level of autonomy in how we build and operate power plants,” said the newly appointed chief AI and robotics officer, Dr. Francesco Borrelli.

This comes after investing over $40 million in acquisitions to enhance solar power plant deployment, reliability, and long-term ROI. This includes OnSight Technology for autonomous survey and fire warning systems, SenseHawk IP to create high-resolution 3D as-built maps of solar project sites, and Amir Robotics to reduce soil-related yield loss.

According to Shugar:

“With millions of sensors and control nodes already deployed over approximately 100 GW of operating systems in 40 countries, Nextracker has a unique opportunity to harness AI and robotics at scale.”

Latest Nextracker Inc. (NXT) Stock News and Developments

Conclusion

Solar energy is one of the most promising and cleanest ways to power the world. Already, solar PV adoption is rising at a fast pace, but of course, the path to renewable energy won’t be dependent on just a single technology.

Hybrid systems that combine photovoltaics, thermoelectrics, and advanced nanomaterials will be key to the future of solar power. 

While material inefficiencies once limited solar thermoelectric technology, it is now breaking barriers through novel thermal management and nanostructuring techniques. The latest breakthrough in STEGs shows that innovation at the material and structural level, not just semiconductor performance, can unlock impressive efficiency gains and help meet rising energy needs.

Click here for a list of top renewable energy stocks.

References:

1. Xu, T., Wei, R., Singh, S.C., et al. 15-Fold increase in solar thermoelectric generator performance through femtosecond-laser spectral engineering and thermal management. Light: Science & Applications, 14, 268, published 12 August 2025. https://doi.org/10.1038/s41377-025-01916-9
2. Zhan, Z., ElKabbash, M., Cheng, J., Zhang, J., Singh, S., & Guo, C. Highly floatable superhydrophobic metallic assembly for aquatic applications. ACS Applied Materials & Interfaces, 11(51), 48512–48517, published 26 December 2019. https://doi.org/10.1021/acsami.9b15540
3. Jalil, S.A., Lai, B., ElKabbash, M., et al. Spectral absorption control of femtosecond laser-treated metals and application in solar-thermal devices. Light: Science & Applications, 9, 14, published 4 February 2020. https://doi.org/10.1038/s41377-020-0242-y