Size-Dependent Colouration Efficiency of Electrochromic Niobium Oxide Smart Windows
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Date
2025
Authors
Dadkhah, M.
Shearer, C.
Jalil, M.A.
Aghili, S.
Losic, D.
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Optical Materials, 2025; 173:117791-1-117791-9
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Mahnaz Dadkhah, Cameron Shearer, M.A. Jalil, Siavash Aghili, Dusan Losic
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Abstract
Electrochromic smart windows with electrochromic coatings, have been developed as a key technology for energy-efficient buildings, enabling dynamic control of light and heat transmission in response to external stimuli. To achieve high-performance electrochromic coatings, nanoscale engineering of materials such as niobium pentoxide (Nb₂O₅) is considered as attractive solution to enhance their optical modulation, charge transport dynamics, and switching efficiency. In this study, we report the size-dependent colouration efficiency of Nb₂O₅ nanostructures synthesized via solvothermal methods using ethanol and benzyl alcohol as solvents and Polyvinylpyrrolidone (PVP) as a surfactant, The prepared materials with particle sizes ranging from 15 nm to 1 μm were deposited onto fluorine-doped tin oxide (FTO) substrates by spray coating to fabricate ∼80 % transparent electrochromic electrodes. These electrodes were assembled into electrochromic devices and evaluated for their charge insertion capacity, switching kinetics, and colouration efficiency. Nb₂O₅ nanostructures characterized by TEM, SEM, XRD, Raman spectroscopy, and UV–Vis analysis revealed that decreasing particle size improved crystallinity and enhanced electrochromic performance. The 15 nm Nb₂O₅ films exhibited the highest Li + diffusion coefficient of 5.37 × 10¯¹⁴ cm² and an optical modulation of 19 % at 700 nm. Furthermore, they showed switching times with a colouration time of 13 s and bleaching time of 3 s, along with a colouration efficiency (CE) of 5.28 cm²/C. In contrast, larger Nb₂O₅ particles (200 nm) exhibited lower performance. These findings highlight the critical influence of particle size and morphology on the electrochromic properties of Nb₂O₅, providing valuable insights into the design of the next-generation smart window coatings through nanostructure control.
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© 2025 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).