Dynamic full-color tunability of high-performance smart windows utilizing absorption-emission effect

The commercialization of vanadium dioxide (VO2) as energy-saving products currently suffers from nonadjustable visible transmittance, resulting in inferior solar regulation efficiency (Delta T-sol<15%), low luminous transmittance (T-lum<60%), and monotonous brown-yellowish appearance. Here, a concept of exploiting all solar spectra for modifying its inherent color as well as synchronously enhancing Delta T-sol has been accomplished on an ultraviolet (UV)-responsive photochromism/VO2 composite film. This structure by itself exhibits low T-lum 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 T-lum. 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.

Automated summary

By incorporating a photosensitive fluorescent layer into the VO2 film, the FPV structure has been developed to enhance solar energy regulation efficiency while changing colors, resulting in a highly transparent film before coloration that can dynamically change colors based on UV light intensity. Furthermore, this structure is able to convert UV light into visible light, blocking UV radiation and increasing luminous transmittance.