An ITO free All Tungsten-Based Electrochromic Energy Storage Device as Smart Window

Area of Science:

• Materials Science
• Energy Storage
• Sustainable Architecture

Background:

• Buildings consume over 30% of energy, primarily for HVAC, necessitating energy-saving solutions.
• Electrochromic Smart Windows (ECSW) reduce energy use but are hampered by high costs (e.g., ITO) and incomplete opacity for privacy.
• Current ECSW technology requires thick films and expensive materials, limiting widespread adoption.

Purpose of the Study:

• To develop cost-efficient and highly opaque Electrochromic Smart Windows (ECSW).
• To explore ITO-free, all-tungsten-based materials for enhanced stability and reduced manufacturing costs.
• To demonstrate the energy storage potential and scalability of the novel ECSW.

Main Methods:

• Fabrication of an ITO-free, all-tungsten ECSW using a 260 nm WO3-x film and a lithium-ion electrolyte.
• Characterization of optical transmittance in the colored state to assess opacity.
• Measurement of areal capacitance and demonstration of powering a liquid crystal display (LCD).
• Testing scalability with a larger 15 × 15 cm2 ECSW using a hybrid electrode.

Main Results:

• The novel ECSW achieved minimal transmittance (≈3%) in the colored state, offering near-full opacity.
• The device exhibited significant areal capacitance (≈13 mF cm-2), capable of powering an LCD for ≈25 minutes.
• A larger-scale prototype confirmed the potential for cost reduction in manufacturing.

Conclusions:

• The ITO-free, all-tungsten ECSW represents a significant advancement in energy-efficient smart window technology.
• This technology offers a cost-effective solution for privacy and energy savings in buildings.
• The developed ECSW has broad applicability in modern architectural designs.