Vanadium dioxide is a promising thermochromic (TC) material owing to its reversible semiconductor-to-metal phase transition, enabling modulation of near-infrared (NIR) transmittance. However, conventional VO 2 -based system typically functions as passive device, relying on ambient temperature changes to induce phase transitions, which limits their responsiveness and controllability in practical applications. In this study, we demonstrate a self-heating TC device by embedding VO 2 in an ITO/Ag/ITO/Glass stack, enabling electrical triggering of TC modulation by Joule heating. To ensure phase purity and stable TC behavior, the VO 2 layer was fabricated using a two-step process: metallic vanadium was first deposited by sputtering, followed by post-annealing in ambient air. This approach provided greater reproducibility and controllability compared to conventional reactive sputtering methods. Through systematic optimization of the annealing temperature and time, we identified the optimal condition for achieving a pronounced and reversible NIR modulation associated with the VO 2 phase transition. The ITO/VO 2 /Ag/ITO multilayer device exhibited distinct TC behavior under both external heating and self-heating via applied voltage. Thermal imaging confirmed the effective and uniform Joule heating performance of the structure, while in-situ transmittance measurements demonstrated successful electrically-driven optical modulation. These results demonstrate the feasibility of a self-heating ITO/VO 2 /Ag/ITO/Glass multilayer as a platform for active smart windows. • Conventional VO 2 -based thermochromic windows operate passively, relying solely on ambient temperature. • Reactive sputtered VO 2 films show poor reproducibility and limited large-area scalability. • Two-step V deposition and annealing enables reproducible VO 2 phase formation. • ITO/Ag/ITO-embedded VO 2 enables efficient Joule-heating-based active control. • Voltage-driven NIR modulation is achieved without external heating.
Kim et al. (Thu,) studied this question.