Abstract: Provided is a photoreactive smart window. The photoreactive smart window includes a liquid crystal layer of which light transmittance changes according to the presence of ultraviolet (UV) light and which is combined with a solar cell. The photoreactive smart window is in a transparent condition in the daytime when UV light is generated from the sun, and accordingly sunlight passing therethrough is converted into electric energy. Also, the photoreactive smart window is in an opaque condition in the evening and at night when no UV light is generated from the sun, and accordingly no curtains are necessary on the windows.