Unveiling the sunshade technology of Xiaomi cars' panoramic sunroofs, which is "more complex than that used in airplanes".

Since the launch of Xiaomi cars, the industry's pursuit of sun protection and heat insulation has been completely ignited.

When the Xiaomi SU7 was released in 2024, Lei Jun spent a significant amount of time talking about the car's overall sun protection. Xiaomi used a multi - layer silver plating process on the sunroof and the front windshield, achieving an isolation rate of 97.6% - 99.9% or more for ultraviolet and infrared rays. The four side windows of the doors are coated with UV - IR coating, and all 5.35 square meters of glass in the car have sun - protection effects.

Some netizens conducted actual tests and found that the interior temperature of the Xiaomi SU7 after being exposed to the sun for 1.5 hours was 12°C lower than that of the Tesla Model 3, which uses enamel coating and ceramic heat - absorbing glass.

The Xiaomi YU7, released in 2025, continues to be upgraded in terms of sun protection and heat insulation. The YU7 Max version comes standard with an intelligent dimming sunroof, which supports adjustment between high - transparency and high - shading states. The isolation rate of ultraviolet and infrared rays reaches 99.99%, and the shading rate reaches 99.85%.

The dimming sunroof has not yet reached the 100% maximum shading rate that a physical sunshade can provide, but it also has advantages that a physical sunshade does not have: Most of the currently available sunshades on the market can only provide shading effects, but the source of heat insulation and sun protection is to block ultraviolet and infrared rays, not just visible light.

Due to the limitations of materials and processes, even if a sunshade can be coated with a sun - protection and heat - insulation layer, it cannot solve the problem that the sunshade becomes a secondary heat source after long - term exposure to the sun.

The dimming sunroof blocks most of the ultraviolet and infrared rays at the source. Without sacrificing headroom, it can provide better sun - protection and heat - insulation effects. All of this is due to a key technological breakthrough in the dimming glass industry.

The dimming sunroof of the Xiaomi YU7 uses EC electrochromic technology. Its principle is to adjust the state of the electrochromic material by changing the voltage, making the glass appear in different states of transparency and shading.

This technology is not new, but due to material and process limitations, it is difficult to cover large - area, high - curvature glass. And the glass mostly appears blue, so it has been rarely considered by the automotive industry in the past.

However, the intelligent dimming sunroof installed in the Xiaomi YU7 allows you to see the stars at night in the high - transparency state and appears neutral black in the high - shading state. With a total area of up to 1.6 square meters and a highly arched shape as a car sunroof glass, the difficulty and craftsmanship of this glass are evident.

The core supplier behind Xiaomi's dimming sunroof is Optics Valley Technology.

This is a company founded in 2017, with R & D centers in Silicon Valley and Shenzhen. It focuses on the R & D and production of technologies such as electrochromic materials and optical films. Its team has gathered many senior technical talents in the field of electrochromism, and many of its members have been deeply involved in this field for more than a decade.

36Kr had an interview with He Jiazhi, the CTO of Optics Valley Technology. He told 36Kr that the hidden champion in the dimming glass industry is an American company that has been established for more than 50 years. The dimming glass of Boeing airplanes is produced by this company. "But they can only make blue glass."

However, in Optics Valley Technology's user research, color is the most important indicator for consumers.

The early products of dimming glass were mostly blue with a hazy texture, which had a low matching degree with the colorful car bodies and interior colors. At the same time, because blue has limited absorption of visible light, blue glass is also more limited in terms of privacy and sun - protection and heat - insulation performance.

He Jiazhi told 36Kr that both car manufacturers and consumers want black glass, but "black" has always been a technical difficulty in the electrochromic material system because it requires higher absorption of visible light.

Xiaomi cars have put forward higher requirements for the isolation rate of ultraviolet and infrared rays and the contrast between light and dark states. To this end, Optics Valley Technology and Xiaomi cars jointly carried out technological breakthroughs and achieved breakthroughs in terms of area, curvature, and light - dark contrast.

"On the Xiaomi YU7, when the dimming sunroof is in the dark state, you can look directly at the sun. The sun will turn into a small dot under the dimming glass. Even in the 40 - degree summer, this is what Mr. Lei meant by 'blocking the sun'." He Jiazhi told 36Kr. "And in the dark shading state, the glass appears as a calm and neutral black."

The application and penetration of intelligent dimming glass in the automotive field reflect the evolution of current market competition: when electrification and intelligence become more accessible, car manufacturers are exploring more technological innovations to create differentiated value.

Whether it is the Xiaomi YU7 using electrochromic technology to solve the pain points of sunroof sun protection, or NIO reducing the volume by 88% and freeing up 8.4 liters of cabin space through a micro - intelligent fuse, market competition has shifted from single performance parameters to a more detailed deconstruction of user scenarios.

This is not only a competition of product strength but also marks that the automotive industry is entering a new stage with "experience" as the core competitiveness. Those who can transform technology into functional values that users can perceive with more precise engineering thinking will be able to build new moats in the market.

The following is the original text of the conversation between 36Kr and He Jiazhi, the CTO of Optics Valley Technology, slightly edited without changing the original meaning:

36Kr: What was the opportunity for the cooperation between Optics Valley Technology and Xiaomi?

He Jiazhi: First of all, the sunroof of the Xiaomi YU7 Max is large in area and has a high arch. For such an irregularly shaped glass, there aren't many dimming technologies to choose from.

Our technology has been continuously iterated. In the early generations of products, while achieving a high - transparency state, there was still room for improvement in the shading ability of the dark state. During the cooperation with NIO, we launched the first black electrochromic dimming glass, which was an upgrade of Optics Valley Technology in color control, meeting the higher requirements of the overall vehicle design for a sense of luxury and privacy.

When we cooperated with Xiaomi, our technology just achieved a breakthrough. You can experience the sunroof of the Xiaomi YU7 Max by yourself. You'll find that you can look directly at the sun when it's in the dark state, even in the 40 - degree summer. As Mr. Lei said, it can "block the sun". The sun becomes a small dot under the dimming glass. And when it's in the bright state, you can see the stars at night.

This technological breakthrough impressed Xiaomi. They thought this value was worth being applied to the car, especially the sun - protection and heat - insulation, which indeed brought a significant difference in user experience.

36Kr: Were these technological breakthroughs completely achieved independently?

He Jiazhi: Actually, we've always wanted to make a breakthrough in this direction. It was quite difficult for us to change the color of the dimming glass from blue to black for the first time because black is extremely challenging. Even the dimming glass on Boeing airplanes is still blue, and its supplier is an American company that has been in the industry for 50 years. This company can be regarded as a hidden champion in the industry, but they can only make blue glass.

So, we were the first to develop black dimming glass. The development process of this technology started with making small - area glass turn black and then progressed to making larger areas turn black. You can think of it like a battery pack. Initially, the capacity was not that large, and we increased it. The sunroof of the Xiaomi YU7 Max is very large, and we need to continuously expand the adjustable range to meet Xiaomi's requirements. The entire process of product development based on these requirements was definitely a co - creation process between us and various car manufacturers.

36Kr: How long did the development process take approximately?

He Jiazhi: It took more than two years. Actually, the most important work during the development cycle was to meet the vehicle - grade requirements. It had to pass a series of tests such as high - and low - temperature tests, and this test cycle alone took six months. If it was just our own product development, it would only take about one year.

36Kr: Some car companies think that data like 99.85% shading rate of dimming glass is not as direct and cost - effective as a physical sunshade. How do you view this concept?

He Jiazhi: In the early years, we mainly targeted what the public considered the early - stage market and worked on many cars. However, this technology hadn't educated the market and users yet. This year, on cars like the YU7 Max, dimming glass has gradually become a standard feature in some high - end models. I think this symbolizes that car manufacturers are willing to pay for this function and experience because dimming glass has indeed solved some pain points.

36Kr: What is the current cost level of a single set of such dimming glass?

He Jiazhi: Cost control is part of our product competitiveness. The specific figures are not yet convenient to disclose.

Currently, there are also some heat - insulation films from certain brands in the aftermarket that can be installed by users themselves. Once these heat - insulation films are installed, the glass will become very dark, which may even affect driving. The cost of applying such a heat - insulation film to the entire car can reach tens of thousands of yuan.

You'll notice that from 2025 onwards, there will be more and more models with dimming glass as a standard feature on the market. The fact that these models come with dimming glass as standard rather than an option actually means that our cost has reached a level that car companies consider to be very cost - effective.

The vision of our company's entrepreneurship is to make dimming technology accessible to every household. So, we definitely need to ensure that cars priced above 150,000 yuan can afford to use dimming glass.

36Kr: What are the differences in the technical routes of the dimming glass of several popular cars on the market?

He Jiazhi: The Zunjie S800 uses LC technology. The characteristic of LC technology is millisecond - level color change. The application of LC technology on the side windows of this car is mainly for privacy functions, such as gesture - controlled dimming. Speed is their advantage.

The Xiaomi YU7 Max uses the fourth - generation EC electrochromic technology of Optics Valley Technology, achieving a shading rate of 99.85%. The biggest highlight of this generation of technology is that it blocks 99.9% of ultraviolet and infrared rays, blocking at the source the main spectra that cause high interior temperatures and interior aging, bringing sun - protection and heat - insulation functions to users.

In the field of intelligent dimming technology, different routes have their own advantages and disadvantages. Our EC electrochromic technology has higher clarity. Although the speed is a bit slower, this "slowness" does not affect normal user use. Moreover, it brings lower energy consumption, stronger sun - protection and heat - insulation, and a better visual experience, which are the aspects we care more about.

36Kr: Can the color - changing speed be optimized? What determines the color - changing speed?

He Jiazhi: In terms of optimization, the color - changing speed is not a bottleneck from an engineering and scientific perspective. Through technological optimization, it can be reduced to 20 - 50 seconds.

And this speed is also related to the area. The Xiaomi YU7 Max uses a sunroof glass of more than 1.7 square meters. We've also developed side - window products. Since the side - window area is small, the perceived color - changing speed is about a dozen seconds.

In our understanding, the color - changing speed is only particularly noticed during the in - store experience or when showing off the car to friends just after buying it. In real - life usage scenarios, users mostly hope that the glass can provide sufficient sun - protection, heat - insulation, and anti - ultraviolet functions, which are more frequently encountered scenarios.

36Kr: What will be the next optimization direction for dimming glass besides the color - changing speed?

He Jiazhi: Color and contrast are the indicators that we will continue to iterate on.

During the Shanghai Auto Show, we conducted a user survey. We randomly surveyed 2,000 users and collected their feedback after experiencing the products. In fact, most people care more about the color.

Glass is a very large interior part in a car. Firstly, its color can't be too flashy; it should be a neutral black or a pure color. Secondly, contrast is important, meaning it should be dark enough when in the dark state and bright enough when in the bright state.

Thirdly, sun - protection and heat - insulation performance are also crucial. Finally, the color - changing speed is considered.

36Kr: Besides privacy and sun protection, will there be more applications for automotive glass in the future?

He Jiazhi: Currently, we've only applied dimming glass to side windows and sunroofs. In fact, the rear windshield, the two front side windows, and the front windshield haven't been covered yet. The dimming glass technology will ultimately evolve towards full - vehicle dimming.

36Kr: Why hasn't full - vehicle dimming been achieved yet?

He Jiazhi: Currently, there are transmittance requirements for the front windshield and front side windows in regulations. But in the future, as we move towards L4 - level autonomous driving, the car will gradually become a third mobile space, and at that time, full - vehicle dimming will become a strong demand.

On the other hand, for other technical routes, such as the dimming technology of liquid - crystal glass, due to the limitations of liquid - crystal molecules, this technology can currently only be applied to glass with relatively small curvature, such as side windows. However, our EC technology can support large - area, large - curvature, and various irregularly shaped glass, which is our advantage.