Electrochromic smart window for modulation of infrared heat

• Main Author: Loke, Jie Yi
• Other Authors: Alfred Tok Iing Yoong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/147818
• Institution: Nanyang Technological University

The majority of global energy generation in our modernised society originates from the burning of fossil fuel which is unsustainable in a long time horizon. Energy consumption in the category of electricity for air-conditioning and indoor lighting in commercial and residential buildings account for about one third of total consumption. It was found that more than half of the heat that enters a building through its windows come from the solar radiation in the near infrared (NIR) region. As a result, in an attempt to lower energy consumption of houses and buildings, smart window technology has been introduced. For a smart window to be function, the material has to exhibit qualities such as dual-band modulation in the NIR and visible range, which permits selective modulation of NIR heat sans influencing visible light transmission. An ideal electrochromic material for the application of smart windows should have high NIR modulation, high visible light transmission, fast switching between bleached and coloured states and excellent long term stability. To meet the functional needs, we proposed a novel Nd-Mo co-doped SnO2/α-WO3 electrochromic material in this project. Compared to conventional SnO2/α-WO3 ECs, our Nd- Mo co-doped SnO2/α-WO3 ECs displays up to 62% NIR modulation (at wavelength 1200nm), 90% visible light transparency (at λ = 600nm), high colouration efficiency (~200 cm2.C−1), fast switching time with minimal electrochromic performance drop of 31% (compared to 59% of undoped sample) following a stability test of 1000 cycles. The improved electrochromic performance is due the existence of Nd-Mo co-dopants that restrict the trapping of Li+ ions within the α-WO3 framework. This reduces the degree of crystallization of α-WO3 layer and improves the electronic conductivity by transferring excess electrons to the conduction band of the SnO2. The current composition of ECs showcased in this report is one of the better electrochromic material to be utilised in the application of smart windows to the best of the author’s knowledge.