Solar Windows: Clear Film for Next-Gen Smart Cities

Nanjing University researchers have unveiled a novel method to power future sustainable cities. Their clear solar panel film can be applied directly to windows during or after the initial manufacturing process. The invention promises to transform passive glass into an efficient form of power generation. Here’s what you need to know.

Traditional Solar Panels and Their Limitations

Combating pollution caused by urban sprawl and industrial factors will require a combination of approaches. One of the most common methods to try to tackle this issue is the use of solar panels.

Photovoltaic cells can convert sunlight into electricity, with the most common forms of the technology being amorphous silicon cells, organic photovoltaics, gallium arsenide, dye-sensitized, and perovskite solar cells.

Problems with Photovoltaic Cells

While photovoltaic options can help to alleviate some of the electricity and pollution concerns, they are not without their limitations. For one, solar panels are fragile components that can become unusable if slightly cracked. Additionally, these devices are expensive to manufacture and require installation in a location with direct sunlight to operate properly.

Source – Pixabay

The latter concern has left many property owners in a dilemma. Do they continue paying exorbitant electricity costs or sacrifice their aesthetics by placing a large number of solar panels on their roof or adjacent space?

Solar Concentrators

One way in which engineers have sought to get around the unsightly look of solar panels is through the use of concentrators. This unique coating leverages nanostructures to concentrate and channel light to the edge of glass panels. From there, the light gets captured by photovoltaic cells built into the edge of the window treatment.

Keenly, the nanostructures guide light waves in the direction of the cells without causing too much visual refraction. This approach enables engineers to build solar panels with different form factors to meet the needs of consumers while retaining the property’s looks.

Problems with Concentrators

To date, the use of concentrators to capture sunlight has encountered several major technical challenges. For one, this strategy requires that photovoltaic cells be located around the edges of the architectural glass. This approach adds to the overall cost and complications required to manufacture these units.

It also makes it very difficult to scale up production. Their complicated manufacturing process and the need to be installed during the first stages of the units’ creation add to the overall cost of producing these devices while detracting from their efficiency and capabilities.

Additionally, both luminescent-type and scattering-type solar concentrators have low efficiency compared to their traditional counterparts. The lowered efficiency comes from several factors, including omnidirectional waveguide-induced factors.

When light hits a concentrator at angles exceeding the critical angle for internal reflection, it never makes it to the photovoltaic cells. The same applies to fluorescent light bands that don’t reflect as well or can produce a haze effect on the glass once applied, rendering them unusable in architectural applications.

Clear Solar Panel Film Study

The study Colorless and unidirectional diffractive-type solar concentrators compatible with existing windows¹ introduces an optimized solar panel design that combines a novel film and concentrator strategy to drive efficiency.

The new solar coating can be applied to any window as a film. This accessibility promises to transform traditional windows into clean energy generators. Best of all, the new approach doesn’t affect window transparency or clarity, making it ideal for use in future buildings and more.

Efficient Solar Capture

To achieve efficient solar capture, the team created colorless transparency solar concentrators capable of harnessing unidirectional light and optimized for wide-angle refraction. This strategy offers ultra-wide-angle solar energy capturing while ensuring seamless integration, while maintaining aesthetic standards.

Source – Photonix

Cholesteric Liquid Crystal (CLC)

At the core of this strategy is the use of a cholesteric liquid crystal (CLC) film. This one-dimensional chiral photonic crystal selectively condenses the circularly polarized light. From there, the light gets refracted via several layers with submicron lateral periodicities.

The material incorporates photoalignment and polymerization techniques to ensure efficiency, relying on a multilayered approach with slanted Bragg planes to direct the light properly. Notably, the film is only 7.5 μm thick and can be applied to any glass surface.

Diffractive Solar Concentrator

Once applied to the window, the solar concentrator goes to work, redirecting polarized sunlight to the window edges so it can be collected by solar cells. Impressively, this approach provides broadband polarization-selective diffraction and waveguiding all without compromising the glass’s clarity.

The team noted that by integrating the concentrator directly into the architectural glass, it reduces the number of photovoltaic cells required by 75%. They also noted that each CLC layer provides an alternate helical pitch, which extends the solar capture capabilities across more light bands.

Architectural Glass

Architectural glass refers to the glass used by builders. It can be found on the side of skyscrapers and in homes globally. Its main characteristics are that it’s transparent and easily installed in properties.

Prototype Testing and Results

As part of the testing stage, the team constructed a small prototype to demonstrate their concept. This device measured 1in diameter and integrated a one-dimensional chiral photonic crystal film coating. From there, the team hooked the device up to a small 10-mW fan.

Notably, the test took place on a sunny afternoon in June and included several different phases. The engineers measure critical aspects, including optical and power conversion efficiency. They noted that the device powered the fan without incident.

Other key results from their testing shed light on crucial factors regarding the use of CLC film. For one, they learned that they could control what edge the light refracts towards by the slant direction of the Bragg planes. By directing more light to cells, the engineers achieved a high average visible transmittance of 64.2%.

They also documented the opacity changes using the color rendering index. The device scored a 91.3, meaning that it retained the majority of its transparency. Impressively, the new solar capture strategy allows up to 38.1% of incident green light energy to be collected at the edge of the window panes.

Clear Solar Panel Film Study Benefits

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There are many benefits that this study brings to the market. For one, there is a strong demand for sustainable energy approaches. This new strategy is the first step towards seamless integration on a large scale. From homes to skyscrapers, this study opens the door for a new level of solar energy capture and clean energy generation.

Transparent

One of the main benefits of this study is that it introduces invisible solar capture methods. Solar panels aren’t the prettiest sight, and those worried about aesthetics, such as architects, will find comfort in knowing that they can design future buildings with sustainability in mind without sacrificing looks.

Economic Benefits

Aside from the money that future solar window users will save, other economic factors make this study a game-changer. For one, it was expensive and time-consuming to build integrated concentrators for windows in the past.

This new strategy reduces manufacturing costs considerably and allows for aftermarket installations of these systems. This practical and cost-efficient approach is designed to meet aesthetic demands while remaining economically viable.

Clear Solar Panel Film Adds Efficiency

The added efficiency gained from these cells can’t be overlooked. Unlike their predecessor, they enable wide-angle, colorless, and unidirectional light capture. The stacked CLC layers integrate optimized helical pitches and submicron-period lateral alignments to direct the potential light energy where it needs to go without any moving parts.

Scalability

Scalability is another major benefit that will help to highlight this technology to the market faster. Until now, using concentrators to improve solar panel energy production has been too complicated and expensive. This latest approach adds scalability to this science, enabling engineers to create massive structures that seamlessly integrate this tech into their core aspects.

Clear Solar Panel Film Study Real-World Applications & Timeline:

There are many applications for clear solar panel film. For one, you can expect to see this approach used in smart cities of the future. The goal is to hit net-zero emissions, and to accomplish this task, engineers will need to integrate sustainable business practices. This option offers both functionality and retains aesthetics.

Sustainable Urban Upgrades

Impressively, the CLC film can be fitted onto existing windows. This option opens the door for a mass retrofitting of solar systems onto current windows to reduce energy demands. Crucially, the film remains stable under long-term exposure and can be applied to nearly any size or shape window.

Urban Agriculture

In the future, greenhouses could generate the power they need to grow plants without any additional sources. This strategy would enable food production nearly anywhere, helping to solve both hunger-related and sustainability problems on a global scale.

Commercialization Timeline

You can expect to see clear solar panel film hitting the market in the next 5-7 years. There is strong demand for this product, and the team has proven that it’s scalable. Now, they will seek out manufacturing partners to help lower production costs, which will help to drive adoption.

Research Team and Funding

Nanjing University hosted a study on clear solar panel films in collaboration with the National Laboratory of Solid State Microstructures, the Key Laboratory of Intelligent Optical Sensing and Manipulation, and the College of Engineering and Applied Sciences. Specifically, the paper lists Dewei Zhang,  Zhenghao Guo, Chun-Ting Xu,  Jianqing Li, Yan-Qing Lu, and Wei Hu as contributors to the project.

Funding for the clear solar panel film study came from several reputable institutions, including the National Key Research and Development Program of China, the National Natural Science Foundation of China, and the Natural Science Foundation of Jiangsu Province.

Clear Solar Panel Film Study Future

The future of clear solar panel film looks bright. The scientists will now work on enhancing broadband efficiency alongside other critical factors. They hope to improve polarization control as part of their next maneuvers. Within the next decade, they seek to utilize this technology to power next-generation greenhouses and more.

Investing in Solar Panel Manufacturing

Several popular manufacturers operate in the solar field. These firms consistently invest in R&D, seeking to transform the industry via efficient and accessible options. As such, these companies drive innovation through their research and development programs. Here’s one company that isn’t scared to innovate and drive sustainable energy options.

NextEra Energy

NextEra Energy entered the market in 1925. At that time, the company went under the name Florida Power & Light Company (FPL). Its goal was to provide much-needed power to Floridians via a variety of options. The company operated power plants, water treatment facilities, and gas storage networks that helped to keep the state active.

In 1997, the company changed its name to FPL Energy. This name change was part of a larger strategy to expand operations out of Florida and across the entire US. In 2009, the company rebranded again into NextEra Energy. This rebrand reflected the company’s newfound focus on sustainable energy options.

Notably, NextEra Energy is the largest producer of wind and solar power in the US currently. It remains a pioneering force in the market. It’s known for its innovative approach, which helped to push solar and thermal energy capture markets forward. Those seeking a well-known and established solar-related stock should consider doing more research into NextEra Energy’s offerings.

Latest NextEra Energy (NEE) Stock News and Performance

Clear Solar Panel Film Study | Conclusion

It’s easy to see why the clear solar panel film study could revolutionize the manufacturing of large-scale urban areas moving forward. Solar power is one of the best ways to supplement energy demands, and this novel approach expands on previous attempts to seamlessly integrate solar power into everyday facilities. As such, this team of engineers deserves credit for their revolutionary approach to solar panel integration.

Learn About Other Sustainability Projects Here.

References:

^{1. .Zhang, D., Guo, Z., Xu, C., Li, J., Lu, Y., & Hu, W. (2025). Colorless and unidirectional diffractive-type solar concentrators compatible with existing windows. PhotoniX, 6(1), 1-12. https://doi.org/10.1186/s43074-025-00178-3}