Design of electrotunable all-weather smart windows

Abstract

Smart windows, capable of selective filtering of solar spectral radiation can help to significantly reduce the energy consumption by heating and cooling systems. However, robust and industry-standard designs of such windows, tunable for all-weather conditions, have been a challenge to date. In this work, we report on the design of ultra-thin electrotunable smart window ‘glasses’ using noble metals as well as their relatively-inexpensive alternatives. We adopt a lithography-free design approach using multilayer metallo-dielectric structure, that can dynamically control the intensity of transmitted solar radiation, depending upon the weather/climate condition. We make use of an electro-optic polymer as dielectric, which on applying voltage, changes the effective refractive index by virtue of electro-optic effect, allowing tunable filtering of visible and infrared radiation over a voltage range of −15 V to +15 V. Our theoretical results are in excellent agreement with those of full-wave simulations. Our design is robust, ultra-thin (60–100 nm thick), large-area compatible, polarization-independent, and angle-insensitive (up to 75 degrees). Aluminium oxynitride based glasses are suitable for designing military-grade, bulletproof, portable, and blast-resistant windows. The figure-of-merit calculations reveal that our relatively-inexpensive metals can outperform industry-standard commercial glasses as well as infrared-blocking plasmonic glasses, reported in the literature.