Vacuum Coating Technology Driving the Electrochromic Glass Industry

1. Introduction

With the advancement of the “dual carbon” strategy and the global energy transition, energy-efficient buildings and green transportation have become irreversible trends. In this context, smart dimming glass has emerged as a key industry focus, with Electrochromic Glass (EC Glass) being the most representative. EC Glass can dynamically adjust its light transmittance and color under an applied electric field, offering energy savings, environmental benefits, and enhanced comfort and intelligence.

According to market research, the global EC Glass market is projected to reach several billion USD by 2030, driven primarily by the building, automotive, and aerospace sectors. However, the realization of EC Glass relies fundamentally on vacuum coating technology. From laboratory research to industrial-scale production, vacuum coating has remained an indispensable core process.

2. Working Principle of Electrochromic Glass

The electrochromic effect is an optical phenomenon based on reversible redox reactions. Materials undergo valence changes under an applied electric field, resulting in changes in light absorption and transmittance. A typical EC Glass structure consists of five to seven layers:

  • Transparent Conductive Layer (TCO):
    Materials such as ITO (Indium Tin Oxide) or FTO (Fluorine-doped Tin Oxide) provide electron pathways while maintaining high transparency.
  • Electrochromic Layer:
    Commonly WO₃ (tungsten oxide). Upon accepting electrons and small ions (e.g., Li⁺, H⁺), W⁶⁺ is reduced to W⁵⁺, changing the layer from colorless to blue.
  • Ion-Conductive Layer (Electrolyte):
    Solid or gel electrolytes conduct small ions while blocking electron flow, enabling reversible electrochemical reactions.
  • Counter Electrode Layer:
    Materials like NiO or V₂O₅ serve as complementary electrochromic layers, enhancing contrast and cycling stability.
  • Rear Conductive Layer:
    Completes the circuit and ensures proper device operation.

EC Glass operates at low voltage (usually <5V), with minimal energy consumption. Once in a certain state, it consumes almost no power. This low-power, reversible, and gradual optical modulation is a key technical advantage.

3. Main Technical Routes and Features

Inorganic Electrochromic Glass

  • Materials: WO₃, MoO₃, NiO, V₂O₅
  • Processes: Magnetron sputtering, evaporation, ALD (atomic layer deposition)
  • Advantages: High stability, large optical modulation, suitable for large-area applications
  • Limitations: Slower response (seconds to minutes), potential degradation over long-term cycling
  • Applications: Building façades, automotive sunroofs, aircraft windows

Organic Electrochromic Glass

  • Materials: Conductive polymers such as PEDOT, PProDOT
  • Processes: Chemical polymerization, solution deposition; vacuum coating can improve film quality
  • Advantages: Fast response, rich color options, multi-tone dimming
  • Limitations: Limited stability, sensitive to humidity and UV
  • Applications: Displays, smart wearables, interior decoration

Hybrid Electrochromic Glass

  • Principle: Combines inorganic and organic materials in multilayer structures
  • Advantages: Combines inorganic durability with organic color versatility
  • Challenges: Interface compatibility and long-term stability
  • Trends: Ideal for multifunctional smart windows; expected to become a mainstream next-generation solution

4. Role of Vacuum Coating Technology in EC Glass

Industrial-scale production of EC Glass relies heavily on vacuum coating, particularly continuous magnetron sputtering technology:

  • Multilayer Functional Film Deposition:
    Precise control of 5–7 functional layers, with nanometer-scale thickness and stable composition/density.
  • Optimization of Optoelectronic Performance:
    Sputtering produces low-resistance, high-transparency conductive layers and regulates WO₃ crystal structure for improved color efficiency.
  • Large-Area Continuous Production:
    Architectural glass often exceeds 2 m². Continuous sputtering lines enable consistent, large-scale output.
  • Integration with Advanced Processes: ALD: Atomic-level thickness control to optimize interface defects; PECVD: Deposition of ion-conductive electrolyte layers

Vacuum coating is not just a fabrication tool; it is a key technology driving both performance enhancement and industrial-scale implementation.

5. Key Application Areas

5.1 Green Buildings

  • Automatic dimming with smooth light transitions
  • Reduces HVAC and lighting energy consumption by 20–30%
  • Case Studies: Bullitt Center (Seattle, USA), Marina Bay Sands Hotel (Singapore)

5.2 New Energy Vehicles

  • Blocks 70–90% of infrared radiation, reducing air-conditioning load and extending driving range by 5–10%
  • Improves comfort and reduces glare
  • Examples: Tesla, Mercedes-Benz EQ series with electrochromic sunroofs

5.3 Aerospace

  • Passengers can independently adjust window transparency, eliminating traditional shades
  • Reduces aircraft weight and energy consumption
  • Example: Boeing 787 Dreamliner

5.4 High-End Displays and Optical Devices

  • Smart mirrors, smart glasses, optical filters
  • Dynamic optical control in photonics and laser systems
  • Anti-glare, energy-saving high-end displays

5.5 Future Potential Applications

  • Smart furniture and interior partitions
  • Photovoltaic-integrated “smart energy windows”
  • Medical and laboratory lighting adjustment
  • Anti-glare consumer electronics screens

6. Advantages and Features

  • Energy Saving & Environmental: Reduces building HVAC energy use by 20–30%; improves EV range by 5–10%
  • Low Power Consumption: Energy only consumed during switching; nearly zero during static state
  • Gradient Dimming: Smooth optical transitions for natural comfort
  • Privacy & Comfort: Adjustable transparency and light control
  • Smart Integration: Compatible with light sensors and automated control systems

7. Challenges and Future Outlook

  • High Cost: Still several times more expensive than standard glass
  • Limited Cycling Life: Some products only support tens of thousands of switches
  • Large-Area Uniformity: Deposition is technically challenging
  • Competing Technologies: SPD and PDLC may replace parts of the market

Future Directions:

  • Novel materials: multivalent oxides, nanocomposites
  • Process breakthroughs: vacuum coating combined with ALD/PECVD
  • Integration with photovoltaics and energy storage for “smart energy windows”
  • Cost reduction and efficiency improvements for widespread adoption

8. Conclusion

Electrochromic glass is rapidly becoming a key material in smart buildings, green transportation, and high-end aerospace applications. Its unique working principle and versatile applications offer enormous growth potential. Vacuum coating technology, especially continuous magnetron sputtering, ensures material performance while enabling industrial-scale production.

SIMVACO, as a leading vacuum coating equipment manufacturer, specializes in high-end PVD, PECVD, and multi-target inline magnetron sputtering systems. Through customized large-scale sputtering and multilayer film solutions, SIMVACO offers the EC Glass industry:

  • High uniformity and large-area coating capabilities for architectural and automotive production
  • Precise multilayer film control to optimize optical performance and cycling life
  • Tailored turnkey solutions from R&D to industrial deployment

With extensive industry experience and advanced vacuum coating technology, SIMVACO is driving the growth of the EC Glass industry, providing reliable core technology support for energy-efficient buildings, smart transportation, and high-end optical applications.

Contact SIMVACO:
Email: simon@simvaco.com
Website: www.simvaco.com

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