Abstract

WO₃-based composite films were fabricated from peroxo-iso-poly tungstic acid and a transparent urethane resin, and the photochromic properties of the films were evaluated under sunlight from three seasons: spring, summer, and winter. All composite films exhibited photochromism under solar irradiation, and the coloring degree of the films varied with the sunlight intensity for each season. We estimate the energy efficiency of the colored composite films for various seasons.

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