Abstract

The commercialization of vanadium dioxide (VO2) as energy-saving products currently suffers from non-adjustable visible transmittance, resulting in inferior solar regulation efficiency (ΔTsol<15%), low luminous transmittance (Tlum<60%), and monotonous “brown-yellowish” appearance. Here, a concept of exploiting all solar spectra for modifying its inherent color as well as synchronously enhancing ΔTsol has been accomplished on an ultraviolet (UV)-responsive photochromism/VO2 composite film. This structure by itself exhibits low Tlum even in a mild UV environment. We further introduce a fluorescence layer on top of photochromic layer to form a three-layer fluorescence/photochromism/VO2 structure (FPV), which could realize the conversion from UV to visible lights there to block most of the UV light and enhance the Tlum. Such FPV films that are optically manipulated display highly transparent before coloration and, further, can dynamically change to other colors according to different intensities of UV light. Moreover, the FPV films result in an increased solar energy regulation ability up to 20.1%, while maintaining 72.6% visible luminous transmittance. These results break shackles of inherent color and exceed the theoretical limit for traditional thermochromic VO2-smart windows, making them easily acceptable for users.

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