Terbium-Doped VO2 Thin Films: Reduced Phase Transition Temperature and Largely Enhanced Luminous Transmittance

Vanadium dioxide (VO2) is a well-known thermochromic material with large IR modulating ability, promising for energy-saving smart windows. The main drawbacks of VO2 are its high phase transition temperature (tau(c) = 68 degrees C), low luminous transmission (T-lum), and weak solar modulating ability (Delta T-sol). In this paper, the terbium cation (Tb3+) doping was first reported to reduce tau(c) and increase T-lum of VO2 thin films. Compared with pristine VO2, 2 at. % doping level gives both enhanced T-lum and Delta T-sol from 45.8% to 54.0% and 7.7% to 8.3%, respectively. The T-lum increases with continuous Tb3+ doping and reaches 79.4% at 6 at. % doping level, representing similar to 73.4% relative increment compared with pure VO2. This has surpassed the best reported doped VO2 thin films. The enhanced thermochromic properties is meaningful for smart window applications of VO2 materials.