Reconfigurable low-emissivity optical coating using ultrathin phase change materials

A team made up of researchers from this department, Physics, Bodle Technologies, Eckersley O'Callaghan Limited and Plasma App Limited considered the problem of how to control the optical properties of a solid-state film over a broad wavelength range. 

Achieving this could have a significant commercial impact, for example with the application of smart glazing technology where near-infrared solar radiation is harvested in the winter and reflected in the summer (this is not possible for materials with fixed thermal and optical properties).

The team experimentally demonstrate in their paper 'Reconfigurable low-emissivity optical coating using ultrathin phase change materials' published in ACS Photonics, the first spectrally tunable, low-emissivity coating using a chalcogenide-based phase-change material (Ge₂₀Te₈₀), which can modulate the solar heat gain of a window while maintaining neutral-coloration and constant transmission of light at visible wavelengths.  

The paper also demonstrates the controlled transfer of absorbed near-infrared energy to far-infrared radiation, which can be used to heat a building's interior and show fast, sub-millisecond switching using transparent electrical heaters integrated on glass substrates.

These combined properties result in a smart window that is efficient and aesthetically pleasing, which the team comment is crucial for successful adoption of green technology.