Facile fabrication of KmCsnWO3 with greatly improved near-infrared shielding efficiency based on W5+-induced small polaron and local surface plasmon resonance (LSPR) modulation

Cesium tungsten bronze (CsxWO3) has potential applications in the field of energy-saving window glasses due to its visible light transparency and near-infrared (NIR) shielding ability. In order to further improve the NIR shielding performance and realize low-cost large-scale production of tungsten bronze, in this work, K, Cs co-doped tungsten bronze (KmCsnWO3, m + n = 0.32) were fabricated by facile solid-state reaction method. It has been clarified that K, Cs co-doping could promote the formation of W5+ and thus enhance the localized surface plasmon resonance (LSPR). Moreover, the K, Cs co-doping is conducive to the formation of single or double bond between W5+ and O, and the double bond W5+=O can increase the strength of small polaron effect and greatly improve the NIR shielding at wavelength 730–1100 nm. Particularly, when K:Cs (mol) = 0.2:0.8, the maximum visible light transmittance of 66.89% and near-infrared shielding rate of 98.25% could be achieved respectively. This work is of great significance for developing CsxWO3 tungsten bronze with improved NIR shielding performance and realizing its industrial production and practical applications in the field of energy-saving windows.