How to properly evaluate and compare the thermochromic performance of VO2-based smart coatings

Abstract

Vanadium dioxide (VO₂)-based thermochromic coatings have been widely studied over four decades, and many studies have been reported to improve their thermochromic performance. Luminous transmittance (T_lum) and solar modulation ability (ΔT_sol) are two important indices to assess the optical performance of VO₂-based smart coatings. However, in many recently reported studies, the ambiguity of thermochromic properties has been observed, which may result in confusion among readers and researchers. In this study, we summarized some recently reported work and attempted to provide a precise and proper definition of the thermochromic performance of VO₂-based smart coatings. A proper evaluation method of thermochromic performance has been proposed to avoid possible ambiguity. Moreover, errors that may occur when measuring thermochromic performance have been provided and should be noted in subsequent study. More importantly, durability and skin comfort have been introduced as important indices to evaluate the performance of VO₂-based smart coatings, which shows practical significance for future study.