Effects of annealing on near-infrared shielding properties of Cs-doped tungsten oxide thin films deposited by electron beam evaporation

• The Cs0.32WO3 thin films were successfully deposited by the electron beam evaporation method.
• The near infrared shielding ability of Cs0.32WO3 thin films were further improved by annealing under H2 atmosphere.
• The Cs0.32WO3 thin films exhibited high transmittance of visible light and high NIR shielding ability.

Near-infrared (NIR) shielding properties are important for solar films. In this study, CsxWO3 films prepared using electron beam evaporation were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and spectrophotometry. The effects of annealing on NIR shielding properties and film microstructure were investigated. The results show that the NIR shielding properties of CsxWO3 films can be improved by annealing at 300–450 °C under pure H2 atmosphere, the amorphous thin films being transformed to crystalline films. The CsxWO3 films annealed at 450 °C in pure H2 atmosphere showed high transmittance of visible light (70%) and high NIR shielding ratio (99%).