Session: 02-04 Building Envelope, Building Energy, and Data Centers

Paper Number: 106197

106197 - Durability-Enhanced Thermochromic Perovskite Smart Window for Energy-Efficient Buildings-Enhanced Thermochromic Perovskite Smart Window for Energy-Efficient Buildings 

The huge energy demand in Hong Kong’s commercial and residential buildings accounts for over 40% of the total primary energy consumption in the city, 50% of which is consumed by heating, ventilation and air-conditioning (HVAC) systems. It should be noted that the heat loss/gain through building envelopes, especially windows, is the main cause of energy consumed by HVAC systems. Therefore, in recent years, various energy-efficient glazing techniques have been developed to manipulate the solar radiation passing through windows and to smartly control the indoor thermal environment. Thermochromic perovskites are of great interest for energy-saving smart windows since they can dynamically and passively change the solar transmittance as the ambient temperature changes. Most importantly, thermochromic perovskites can be easily and cost-effectively coated on windows by a solution-based coating method. However, thermochromic perovskites also face a key problem in that they can be easily damaged by water and/or moisture in the ambient air. So, thermochromic perovskite is required to be sealed in a double-glazed window to strictly control the surrounding humidity. To solve this problem, in this study, a durability-enhanced thermochromic perovskite smart window is proposed. A unique three-layer structure is developed for this window, in which the bottom layer is the thermochromic perovskite to achieve the thermochromism of the window. The middle layer is an inorganic buffer layer to control the influence of water vapor on the thermochromic perovskite and at the top is a nano silica hydrophobic layer to repel the water droplet efficiently to prevent corrosion of the thermochromic perovskite by water. This new thermochromic perovskite window demonstrates an excellent optical performance with a high luminous transmittance of ~85% in a transparent state, a high solar modulation ability (Δτ_sol) of ~24%, and a low haze of ~20%. In addition, the new thermochromic perovskite window has a superhydrophobic surface with a contact angle of 160^o, thus the water can be easily removed, making it water-proof. Most importantly, it is shown that the new thermochromic perovskite window maintained a high solar modulation ability (Δτ_sol >20%) after a 45 day durability test in an ambient environment with ~60% relative humidity, representing ~20 times the lifetime of an unprotected thermochromic perovskite window. Overall, the proposed novel window structure provides an easy and effective strategy to improve the lifetime of thermochromic perovskite, further paving the way for practical applications of thermochromic perovskite in energy-efficient smart windows.

Presenting Author: Sai Liu City University of Hong Kong

Presenting Author Biography: Dr. LIU is a Postdoctoral Fellow in School of Energy and Environment, City University of Hong Kong. His research is the novel envelopes for building energy conservation with respect to indoor heat gain regulation. In the last 5 years, he focused on investigating thermochromic smart windows and developed thermal responsive color-switchable perovskite windows for building applications. Some representative works have been published on Advanced Functional Materials and Advanced Science as the cover.