Lattice stress engineering induced by rare-earth ion in regulating phase transition and thermochromic properties of VO2 films

Samarium-Doped Vanadium Dioxide Thin Films to Modulate the Thermochromic Properties for Energy-Saving Smart Windows

“…On the other hand, the narrowing of E g1 is responsible for lowering of NIR transmittance in S1–S4 at 20 °C. Shrinking of E g1 favors phase transition of the M 1 phase to the R phase at lower temperature by reducing the excitation energy of electrons from the d ∥ band to π* band according to refs and ; however, Sm doping does not reduce T MIT following E g1 . These results are in good agreement with our previous computational study about RE-doped VO 2 …”

“…Various techniques have been adopted to deal with the mentioned issues. Ion doping, − strain engineering, , defect engineering, , external electric fields, ,− and plasmonic particle incorporation were found effective in reducing T MIT , among which ion doping is the most popular approach to lowering T MIT , because other strategies have a limited effect on T MIT reduction. Ion doping produces strain in the lattice due to the difference in size between dopants and host atoms as well as changes the carrier concentration because dopants have different numbers of valence electrons than host atoms of VO 2 to benefit thermochromic performance and play the role of strain or defect engineering.…”

Enhancing Thermochromic Properties for Thermal Regulation: A Synergistic Study of Er–W-Codoped Vanadium Dioxide (VO2)

“…38−40 Interestingly, some studies involving codoping of W and Mo with low-valent rare-earth (RE) elements deviated from the conventional concept of charge compensation, and these results confused the reader in grasping the underlying metal− insulator transition (MIT) mechanism. 22,40,41 Er, a low-valent cation, is one of the RE elements that proved itself better for improving T MIT , Tr lum , and ΔTr sol simultaneously in our previous study and exhibited the best performance at 4 atomic percent (at. %) doping.…”

“…It has applications in photothermal, radiative cooling, ,, thermochromic smart window, − optical switching, , and other fields. − The primary function of VO 2 -based thermochromic windows is to control NIR transmittance, which modifies the building’s solar heat uptake in winter and summer to keep the room at ambient temperature. However, high phase transition temperature ( T MIT ), lower visible transmittance Tr lum , poor solar modulation ability (Δ Tr sol ), and correct understanding of the phase transition mechanism are important issues of VO 2 -based thermochromic windows, and various approaches such as strain engineering, − defect engineering, , ion doping, − microroughness, biomimetic nanostructure, and nanoporosity are used to deal with these problems, from which ion doping is considered a multifunction technique to tune properties. The high-valent W dopant efficiently reduces the T MIT to room temperature or even lower but compromises optical properties and decreases long-wave IR emittance modulation .…”

“…The simultaneous doping of W with low-valent doping ions, e.g., Mg, Al, and Eu, led to a synergistic enhancement of Tr lum . However, the beneficial synergy effect on reducing T MIT was compromised due to charge compensation as the low-valent dopant content increased. − Interestingly, some studies involving codoping of W and Mo with low-valent rare-earth (RE) elements deviated from the conventional concept of charge compensation, and these results confused the reader in grasping the underlying metal–insulator transition (MIT) mechanism. ,, …”