Smart, Sustainable, and Affordable: India’s TiO₂-Based Smart Windows Breakthrough

In their latest research published in the journal Small, Dr. Ashutosh K. Singh and his team at CeNS proposed a low-cost alternative using titanium dioxide (TiO₂) films and aluminum-ion-based electrolytes.

In a major leap towards affordable and sustainable infrastructure, scientists from India’s Centre for Nano and Soft Matter Sciences (CeNS)—an autonomous institute under the Department of Science and Technology (DST)—have developed a novel, cost-effective electrochromic smart window that not only changes colour with an electric stimulus but also stores energy. This innovation could significantly reduce the cost of smart window technology, making it accessible to a wider market and pushing forward the vision of zero-energy buildings.

The Promise of Smart Windows in Sustainable Architecture

Smart windows are a hallmark of green building design. They regulate indoor temperatures by controlling the amount of light and heat entering a space, thereby reducing the need for air conditioning or artificial lighting. These windows are electrochromic, meaning they alter their transparency or color in response to a small applied voltage. By doing so, they block visible and near-infrared (NIR) light, substantially decreasing heat gain in buildings.

Traditionally, such windows are made using tungsten oxide (WO₃) and lithium-based electrolytes—materials that, while effective, are expensive and resource-limited. This has kept smart windows out of reach for widespread, cost-sensitive deployment in residential and commercial buildings.

Game-Changing Materials: TiO₂ and Aluminum-Based Electrolytes

In their latest research published in the journal Small, Dr. Ashutosh K. Singh and his team at CeNS proposed a low-cost alternative using titanium dioxide (TiO₂) films and aluminum-ion-based electrolytes. These materials are earth-abundant, safe, and significantly cheaper, offering a promising solution to bring smart window technology to scale.

Though TiO₂ has long been known for its electrochromic behavior, it has been underutilized due to its low coloration efficiency—a critical metric that measures the optical density change per unit of electrical charge. The CeNS team overcame this limitation by introducing engineered oxygen vacancies in the TiO₂ film, which dramatically improved its electrochromic response.

Remarkable Performance and Energy Storage in One Device

The result was a dual-functional smart window that not only switches between transparent and tinted states effectively but also stores electrical energy. Key performance metrics from the study include:

• Coloration efficiency of 27 cm²/C—among the highest ever reported for TiO₂.

• Transmittance modulation:

  • 55% for total solar light

  • 47% for visible light (luminous)

  • 41% for near-infrared (NIR)

• Film thickness of just ~340 nm, demonstrating material efficiency.

• Real capacitance of 34 mF/cm², enabling robust energy storage.

• Cycling stability of 96% capacity retention over 2000 cycles, which is critical for long-term performance in buildings.

These dual-functional devices are not only intelligent in regulating indoor environments but also act as energy storage units, capable of integrating with solar systems and other sustainable energy solutions.

Towards Widespread Adoption and Zero-Energy Buildings

By using affordable and scalable materials, this innovation addresses a long-standing barrier in the commercialisation of electrochromic smart windows. The team’s findings pave the way for wider adoption in homes, office complexes, and smart cities, where energy conservation and sustainable design are no longer optional but essential.

The CeNS breakthrough is particularly timely as India and other countries move towards net-zero energy goals in architecture. Smart windows such as these can become integral components of zero-energy buildings (ZEBs), contributing to both passive and active energy efficiency.

This landmark research led by Dr. Ashutosh K. Singh represents a significant stride in materials science and clean technology. With smart windows that are now affordable, energy-efficient, and durable, the dream of sustainable living spaces is no longer futuristic—it is becoming reality.