Optimizing Thermochromism of Solution-Processed VO$_2$ Nanocomposite Films for Chromogenic Fenestration

TL;DR

This study develops a cost-effective VO₂-In₂O₃ nanocomposite film with enhanced luminous transmittance and strong thermochromism, advancing the application of thermochromic fenestration technologies.

Contribution

It introduces a novel VO₂-In₂O₃ nanocomposite film with optimized optical properties and reduced production costs, demonstrating significant improvements over existing materials.

Findings

VO₂-In₂O₃ films show strong thermochromism

Solution processing reduces manufacturing costs by 4-7 times

In₂O₃ diluent enhances luminous transmittance without affecting thermochromism

Abstract

Vanadium (IV) oxide is one of the most promising materials for thermochromic films due to its unique, reversible crystal phase transition from monoclinic (M1) to rutile (R) at its critical temperature (T$_c$) which corresponds to a change in optical properties: above T$_c$, VO$_2$ films exhibit a decreased transmittance for wavelengths of light in the near-infrared region. However, a high transmittance modulation often sacrifices luminous transmittance which is necessary for commercial and residential applications of this technology. In this study, we explore the potential for synthesis of VO$_2$ films in a matrix of metal oxide nanocrystals, using In$_2$O$_3$, TiO$_2$, and ZnO as diluents. We seek to optimize the annealing conditions to yield desirable optical properties. Although the films diluted with TiO$_2$ and ZnO failed to show transmittance modulation, those diluted with In$_2$O$_3$ exhibited strong thermochromism. Our investigation introduces a novel window film consisting of a 0.93 metal ionic molar ratio VO$_2$-In$_2$O$_3$ nanocrystalline matrix, demonstrating a significant increase in luminous transmittance without any measurable impact on thermochromic character. Furthermore, solution-processing mitigates costs, allowing this film to be synthesized 4x-7x cheaper than industry standards. This study represents a crucial development in film chemistry and paves the way for further application of VO$_2$ nanocomposite films in chromogenic fenestration.