Infrared optical properties modulation of VO2 thin film fabricated by ultrafast pulsed laser deposition for thermochromic smart window applications

Abstract

Over the years, vanadium dioxide, (VO2(M1)), has been extensively utilised to fabricate thermochromic thin films with the focus on using external stimuli, such as heat, to modulate the visible through near-infrared transmittance for energy efficiency of buildings and indoor comfort. It is thus valuable to extend the study of thermochromic materials into the mid-infrared (MIR) wavelengths for applications such as smart radiative devices. On top of this, there are numerous challenges with synthesising pure VO2 (M1) thin films, as most fabrication techniques require the post-annealing of a deposited thin film to convert amorphous VO2 into a crystalline phase. Here, we present a direct method to fabricate thicker VO2(M1) thin films onto hot silica substrates (at substrate temperatures of 400 °C and 700 °C) from vanadium pentoxide (V2O5) precursor material. A high repetition rate (10 kHz) femtosecond laser is used to deposit the V2O5 leading to the formation of VO2 (M1) without any post-annealing steps. Surface morphology, structural properties, and UV–visible optical properties, including optical band gap and complex refractive index, as a function of the substrate temperature, were studied and reported below. The transmission electron microscopic (TEM) and X-ray diffraction studies confirm that VO2 (M1) thin films deposited at 700 °C are dominated by a highly texturized polycrystalline monoclinic crystalline structure. The thermochromic characteristics in the mid-infrared (MIR) at a wavelength range of 2.5–5.0 μm are presented using temperature-dependent transmittance measurements. The first-order phase transition from metal-to-semiconductor and the hysteresis bandwidth of the transition were confirmed to be 64.4 °C and 12.6 °C respectively, for a sample fabricated at 700 °C. Thermo-optical emissivity properties indicate that these VO2 (M1) thin films fabricated with femtosecond laser deposition have strong potential for both radiative thermal management or control via active energy-saving windows for buildings, and satellites and spacecraft.

Smart thermally responsive perovskite materials: Thermo-chromic application and density function theory calculation

“…Therefore, the smart window device can not only work in the visible light range, it should also have a certain blocking and modulation ability for infrared light. However, most perovskite materials do not work well in the NIR range, so how to improve their NIR modulation ability has become a popular research direction [ 44 , [96] , [97] , [98] , [99] ].…”

Thermochromic Smart Windows Assisted by Photothermal Nanomaterials

“…Vanadium dioxide (VO 2 ) is a kind of metal-insulator phase transition (MIT) material, which is extensively utilized in thermochromic smart windows [ 13 , 14 , 15 , 16 ]. Its phase transition temperature is close to room temperature at 68 °C [ 17 ].…”

Optimal Design and Analysis of 4.7 μm Hybrid Deep Dielectric High Efficiency Transmission Gratings

“…SiO 2 is a low refractive index material with great firmness and damage resistance and a good fit with Si and Ge [ 12 ]. The optical film theory [ 13 ] calculates the refractive index of the film material at 4.7 μm based on deposition tests of Si, Ge, and SiO 2 single-layer films to be n(Si) = 2.92, n(Ge) = 3.88, and n(SiO 2 ) = 1.40.…”