Since the debut of Xiaomi’s first car, the automotive sector’s attention to sun protection and heat insulation has increased.
When Xiaomi launched the SU7 in 2024, CEO Lei Jun dedicated a substantial portion of his presentation to the vehicle’s sun protection features. The SU7’s panoramic glass roof and windshield used a multi-layer silver coating that blocked 97.6–99.9% of ultraviolet (UV) and infrared (IR) rays. All four side windows received the same coating, giving the car’s 5.35 square meters of glass uniform protection.
Independent tests found that after 1.5 hours of direct sunlight, the interior of a Xiaomi SU7 was 12 degrees Celsius cooler than a Tesla Model 3, which uses glazed and ceramic heat-absorbing glass.
In 2025, Xiaomi introduced the YU7, raising the standard for sun and heat protection. The YU7 Max came with an intelligent dimmable panoramic roof capable of switching between high-transparency and high-shading modes. It blocked 99.99% of UV and IR rays and achieved a shading rate of 99.85%.
While this did not match the complete blackout of a physical sunshade, it offered benefits conventional shades could not. Most sunshades block visible light but still allow UV and IR radiation—the primary causes of heat buildup and material aging—to pass through. Applying insulating films to physical sunshades can reduce this effect, but the shades themselves can still become secondary heat sources after prolonged exposure. Dimmable glass intercepts most harmful rays at the source, without reducing headroom, and improves thermal comfort. This advance was enabled by a key improvement in electrochromic (EC) glass technology.
The YU7’s panoramic roof changes transparency by varying the voltage applied to electrochromic materials. While the concept is established, earlier limitations in materials and manufacturing hindered its application to large, curved automotive glass. Previous products often had a blue tint, limiting their appeal.
The YU7 Max’s roof maintains a neutral black tint in its high-shading mode and provides clear visibility, including of the night sky, in high-transparency mode. Covering 1.6 square meters with a pronounced arch, it reflects both engineering and manufacturing complexity.
The technology was developed by Ambilight, founded in 2017 with R&D centers in Silicon Valley and Shenzhen. The company specializes in electrochromic materials and optical films, with a team experienced in the field for more than a decade.
In an interview with 36Kr, Ambilight CTO He Jiazhi noted that a major US electrochromics supplier, known for producing Boeing aircraft glass, has only achieved blue-tinted versions.
Ambilight’s research found color to be the most important factor for automotive buyers. Early blue-tinted products clashed with vehicle paint and interiors, offered limited privacy, and provided weaker thermal insulation. Black glass was preferred, but achieving it required significantly higher visible light absorption, a longstanding challenge in electrochromic materials. Xiaomi’s requirements for UV and IR rejection and contrast led Ambilight to make breakthroughs in size, curvature, and brightness control.
“In the YU7 Max’s dark mode, you can look straight at the sun, even in 40 degrees Celsius heat,” He said. “The sun appears as a small dot, and in bright mode, you can see the stars at night.”
The adoption of intelligent dimmable glass highlights a shift in automotive competition. As electrification and smart systems become standard, automakers are focusing on innovations that create measurable differences in user experience.
Whether it is Xiaomi addressing cabin heat through electrochromics or Nio redesigning a smart fuse to free 8.4 liters of cabin space, competition is moving from performance specifications to engineering features that improve real-world use. The industry is entering a phase where experience is a primary competitive factor, and the most successful companies will be those that translate engineering precision into tangible customer benefits.
The following transcript has been edited and consolidated for brevity and clarity.
36Kr: What was the starting point for the collaboration between Ambilight and Xiaomi?
He Jiazhi (HJ): The YU7 Max roof is very large and has a high arch. For irregularly shaped glass like that, there are few dimming technologies available.
Our technology has been evolving. Earlier generations achieved a high-brightness transparent state, but the shading performance in dark mode needed improvement. When we worked with Nio, we launched our first black electrochromic dimmable glass. That was an upgrade in color control, meeting higher standards for a premium feel and privacy.
By the time we began working with Xiaomi, we had just made a breakthrough. In the YU7 Max’s dark mode, you can look straight at the sun, even in 40 degrees Celsius heat. As Lei Jun said, it blocks the sun. The sun appears as a small dot, and in bright mode, you can see the stars at night.
That capability aligned with Xiaomi’s focus on tangible improvements in user experience, particularly in sun protection and heat insulation.
36Kr: Were these breakthroughs developed entirely in-house?
HJ: We had long aimed to achieve black dimmable glass, which is extremely difficult to produce. Even now, Boeing aircraft use only blue-tinted dimmable glass, supplied by a US company that has been in the field for over 50 years. You could call them a hidden champion, but they can only make blue.
We were the first to develop black dimmable glass. Initially, we could only produce small pieces, then gradually scaled up. It was like building bigger battery packs. The capacity had to grow to match the YU7 Max’s roof size. Defining requirements and developing the product was a co-creation process with several automakers.
36Kr: How long did the development process take?
HJ: More than two years. The longest stage was meeting automotive-grade standards, such as high- and low-temperature testing. One round of these tests takes six months. Without them, development would have taken about a year.
36Kr: Some automakers say a 99.85% shading rate still cannot match a physical sunshade, which is more direct and cheaper. What’s your view?
HJ: Early on, we were in an immature market, equipping cars before users understood the value. Now, with models like the YU7 Max, dimmable glass is becoming standard on high-end trims. That shows automakers are willing to pay for the feature because it solves real problems.
36Kr: What does this type of glass cost?
HJ: Cost control is part of our competitiveness, but I can’t share exact figures. In the aftermarket, thermal insulation films can be so dark they affect driving, and applying them to an entire car can cost more than RMB 10,000 (USD 1,400).
Starting in 2025, more cars will include dimmable glass as standard rather than optional. That means costs are now at a level automakers find acceptable. From the beginning, our vision was to make dimming technology accessible to a broad market, so any car priced above RMB 150,000 (USD 21,000) should be able to use it.
36Kr: How do dimmable glass technologies differ among popular models?
HJ: The Maextro S800 uses liquid crystal (LC) technology, which can change color in milliseconds. It’s mainly used for side windows and privacy features such as gesture-controlled dimming. Speed is its advantage.
The Xiaomi YU7 Max uses our fourth-generation EC technology, with a 99.85% shading rate. The key feature is blocking 99.9% of UV and IR light, cutting the wavelengths that cause heat buildup and interior aging. This delivers real sun protection and heat insulation.
Every technology has pros and cons. Our EC technology offers higher clarity. It changes more slowly, but that does not affect normal use. In return, it consumes less energy, offers stronger protection, and provides a better visual experience.
36Kr: Can switching speed be improved?
HJ: Switching speed is not a bottleneck. With optimization, we can reach 20–50 seconds. Size matters. The YU7 Max’s roof is over 1.7 square meters, while side windows change in just over ten seconds.
In practice, users prioritize sun protection, heat insulation, and UV blocking over switching speed, which tends to stand out only in showroom settings or demonstrations.
36Kr: Beyond switching speed, what’s the next focus for optimization?
HJ: Color and contrast. At Auto Shanghai, we surveyed 2,000 visitors. Most said color was most important.
On a car, glass covers a large visual area. First, the color should be neutral black or a pure tone. Second, contrast matters: dark mode must be dark enough, and bright mode bright enough. Third comes sun protection and heat insulation. Switching speed ranks lower.
36Kr: Besides privacy and sun protection, will automotive glass gain more functions?
HJ: So far, we’ve applied dimming to side windows and roofs. Rear windshields, front side windows, and front windshields have not yet been implemented. Ultimately, we expect full-vehicle dimming.
36Kr: Why hasn’t full-vehicle dimming been achieved yet?
HJ: Front windshields and side windows face legal light transmittance requirements. As we move toward Level 4 autonomous driving, cars will become a “third mobile space,” which will create strong demand for full-vehicle dimming.
For LC technology, molecular limitations restrict it to flat glass, such as side windows. Our EC technology works on large areas, high curvature, and irregular shapes. That’s our advantage.
KrASIA Connection features translated and adapted content that was originally published by 36Kr. This article was written by Xu Caiyu for 36Kr.