ScholarWorks@중앙대학교

초록

Monoclinic vanadium dioxide (VO2(M)) is a thermochromic material for energy-saving smart windows due to its sharp metal–insulator transition (MIT), which enables dynamic regulation of solar energy input. However, VO2(M) has limitation for practical applications by its unaesthetic intrinsic brownish hue that originates from its narrow optical bandgap. In this study, we demonstrate dynamically tunable, colored thermochromic smart films composed of VO2(M) nanoparticle (NP) and polyvinylpyrrolidone (PVP) composites deposited on silver (Ag) thin-films. Colloidal VO2(M) NPs, synthesized via a single-step, annealing-free hydrothermal method. The NPs were mixed with PVP to form colloidally stable inks, enabling room-temperature, solution-processed deposition. VO2(M)–PVP composite thin films were deposited onto Ag thin films on flexible polymer substrates to form bi-layered Fabry–Pérot structures that generate vivid interference colors. The visible colors and near-infrared (NIR) transmittance could be modulated by varying temperature and humidity; this property was attributed to thickness variations owing to the hygroscopic behavior of PVP and phase transition of VO2(M) NPs. A wide range of visible colors can be achieved by adjusting the thickness of the VO2(M)–PVP cavity. The flexible films proposed herein can be directly integrated onto existing buildings and curved automotive windows without requiring high-temperature processing. Their practical feasibility was further demonstrated through laboratory-scale mock-house tests and energy-saving simulations. This combination of customizable hue, high luminous transparency, effective solar modulation ability, and processibility highlights their potential for applications in the next generation of energy-saving smart windows.

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