Key Takeaways & Executive Findings
- •• A flexible dual-band electrochromic device achieves high optical modulation (73.1% at 633 nm, 85.3% at 1200 nm) and long cycle life (3.3% capacity loss after 10,000 cycles). • The device independently modulates visible and near-infrared light through three distinct modes, offering superior energy-saving performance compared to commercial low-emissivity glass in most global climates. • Integrating energy storage, the device exhibits high capacitance and an energy recycling efficiency of 51.4%, enabling local reuse of energy consumed during coloration. • The nanowire structure and oxygen vacancies of oxygen-deficient tungsten oxide provide excellent flexibility and durability, making the device suitable for practical smart window applications.
Abstract
Dual-band electrochromic devices capable of the spectral-selective modulation of visible (VIS) light and near-infrared (NIR) can notably reduce the energy consumption of buildings and improve the occupants’ visual and thermal comfort. However, the low optical modulation and poor durability of these devices severely limit its practical applications. Herein, we demonstrate an efficient and flexible bifunctional dual-band electrochromic device which not only shows excellent spectral-selective electrochromic performance with a high optical modulation and a long cycle life, but also displays a high capacitance and a high energy recycling efficiency of 51.4%, integrating energy-saving with energy-storage. The nanowires structure and abundant oxygen-vacancies of oxygen-deficient tungsten oxide nanowires endows it high flexibility and a high optical modulation of 73.1% and 85.3% at 633 and 1200 nm respectively. The prototype device assembled can modulate the VIS light and NIR independently and effectively through three distinct modes with a long cycle life (3.3% capacity loss after 10,000 cycles) and a high energy-saving performance (8.8 °C lower than the common glass). Furthermore, simulations also demonstrate that our device outperforms the commercial low-emissivity glass in terms of energy-saving in most climatic zones around the world. Such windows represent an intriguing potential technology to improve the building energy efficiency.
1. Introduction
Buildings consume ~40% of global energy consumption, and as high as ~50% of this energy is presently used for indoor thermal and visual management (e.g., heating, cooling and lighting) [1, 2]. Windows, as the primary means of energy exchange between the interior and exterior environments, play an important role in building energy efficiency because that 20%–40% of energy used in heating and cooling is lost through windows [3–5]. It is therefore imperative to develop energy-efficient windows for green and zero-carbon buildings. Electrochromic smart windows have emerged as an attractive technology to reduce the building’s energy consumption by up to 20% than common windows through dynamically and reversibly modulating the transmittance of solar radiation [6–19].
The solar radiation consists of ultraviolet (UV), visible light (VIS, 400–780 nm) and near-infrared (NIR, 780–2500 nm), and the NIR energy accounts for ~43% of the total solar irradiance [20–24]. Therefore, the NIR modulation and NIR-selective modulation of the smart windows have a remarkable effect on the energy consumption, and indoor occupant comfort of the buildings [25–27]. However, many of the reported electrochromic smart windows can only provide VIS modulation, or block VIS and NIR without any spectral selectivity. Dual-band electrochromic smart windows, which could modulate the VIS and NIR independently and dynamically through bright, cool and dark modes, have been introduced as a promising energy-efficient technology for improving the building energy efficiency [28–39]. The energy consumption of buildings can be further lower up to 10%–20% than traditional electrochromic smart windows through the smart regulation of solar light and solar heat into buildings.
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Zekun Huang, Yutao Peng, Jing Zhao, Shengliang Zhang, Penglu Qi, Xianlin Qu, Fuqiang Yan, Bing Ding, Yimin Xuan, Xiaogang Zhang (2024). An Efficient and Flexible Bifunctional Dual-Band Electrochromic Device Integrating with Energy Storage. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01604-0
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Frequently Asked Questions
What is a dual-band electrochromic device?
A dual-band electrochromic device is a smart window technology that can independently modulate visible light and near-infrared radiation, allowing for separate control of brightness and heat, thereby improving energy efficiency and occupant comfort.
How does the device achieve high optical modulation?
The device uses oxygen-deficient tungsten oxide nanowires with abundant oxygen vacancies, which provide a large surface area and enhanced electrochromic properties, resulting in high optical modulation of 73.1% at 633 nm and 85.3% at 1200 nm.
What is the energy recycling efficiency of the device?
The device demonstrates an energy recycling efficiency of 51.4%, meaning it can recover and reuse over half of the energy consumed during the coloration process, contributing to overall energy savings.
How does the device compare to commercial low-emissivity glass?
Simulations show that the device outperforms commercial low-emissivity glass in terms of energy-saving performance in most climatic zones around the world, making it a more effective solution for reducing building energy consumption.
What are the potential applications of this technology?
The flexible and bifunctional nature of the device makes it suitable for smart windows in buildings, as well as potential applications in wearable electronics, displays, and energy storage systems, offering both energy-saving and energy-storage capabilities.
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