Mg-Ni-H films as selective coatings: tunable reflectance by layered hydrogenation

TL;DR

Mg-Ni-H films exhibit large, tunable changes in reflectance due to layered hydrogenation, making them promising for smart solar coatings with adjustable optical properties.

Contribution

This work reveals a self-organized layered hydrogenation mechanism in Mg-Ni-H films that enables tunable interference-based reflectance for solar applications.

Findings

Large reflectance changes at different hydrogen contents

Reflectance patterns are interference-based and tunable by film thickness

High absorptance contrast between solar and thermal energies

Abstract

Unlike other switchable mirrors, Mg2NiHx films show large changes in reflection that yield very low reflectance (high absorptance) at different hydrogen contents, far before reaching the semiconducting state. The resulting reflectance patterns are of interference origin, due to a self-organized layered hydrogenation mechanism that starts at the substrate interface, and can therefore be tuned by varying the film thickness. This tunability, together with the high absorptance contrast observed between the solar and the thermal energies, strongly suggests the use of these films in smart coatings for solar applications.