The Effect of CeO2 Antireflection Layer on the Optical Properties of Thermochromic VO2 Film for Smart Window System

CeO-VO bilayer structure was fabricated to investigate the effect of depositing CeO film on the optical properties of VO film for smart window application. CeO was employed as an antireflection (AR) layer material of VO film because of its advantages which include high transparency in the visible-near infrared range and high refractive index. All the films were deposited on soda-lime glass substrate by pulsed laser deposition method. Optical calculations were carried out using transfer-matrix method for the purpose of designing CeO-VO bilayer structure with enhanced integrated luminous transmittance ( ) and switching efficiency (Δ ). The optical constants of VO and CeO films needed for the optical calculation were measured by spectroscopic ellipsometer. The curve of the shape of which depends on the thickness of CeO layer, was calculated in each VO sample, which showed two maxima. The samples were divided into two groups; one for the highest enhancement of and the other for balanced enhancement between and Δ . The sample with the structure of ~60 nm CeO AR layer on 39-nm thick VO film showed large increase of (~27%) with Δ of ~5%, which is the largest increase in reported so far. Two samples in the other group showed the balanced enhancement in (~57, ~50%) and Δ (~9, ~10.5%). The effect of CeO AR layer on the optical properties of VO film was confirmed with the optical calculation and the experimental results. CeO-VO bilayer structure showed notable improvement of optical properties compared to the single VO film, indicating that CeO layer can be effectively used as the antireflection layer while working as a protective layer that can prevent the oxidation of VO layer as well.