The thickness of the coated layer is related to the total volume of the layer of Cs0.33WO3 nanoparticles. Particularly, the spectra of the two different films have a significant deviation in the range of UV to NIR region, which implies that the number density of the nanoparticles in the double layer is larger than that of composite-coated layer in the same number. Figure 6 Cross-sectional images and spectra of the

Cs 0.33 WO 3 -coated films. The cross-sectional SEM and TEM images of the Cs0.33WO3 -coated film fabricated by composite layer (a, b) and double layer coating method (c, d) and spectra of the films Y-27632 mouse fabricated by different methods from UV to NIR region (e), respectively. Moreover, the haze was measured using the drying conditions of each film as stated in Table 3 to analyze the processability of the coated film. High haze was PLX4032 order observed in the composite layer-coated film under typical thermal drying conditions.

While the haze value of coating film depends on somewhat subjective conditions, such as the surface roughness and type and composition ratio of the dispersants in the coated materials [22], however, low haze could be detected using thermal drying under vacuum. Meanwhile, in a double layer-coated film constructed from layers containing individual materials, the lowest haze of the film was observed compared to that from the composite layer coating due to the absence of surface roughness by nanoparticles in the surface as shown in SEM cross-sectioned images. Thus, from the perspective of haze value, the double layer-coated film is less sensitive to the effect of surface roughness.

Table 3 Haze values by varying the drying conditions ID-8 and different coating methods   Double layer-coated film dried at 80°C Composite layer-coated film dried at     80°C 90°C 100°C 100°C (vacuum oven) Haze value <1.00 7.28 5.28 3.76 1.07 Conclusions Using a LTS model based on the Mie-Gans theory, double layer reflection, and Rayleigh scattering, this study quantitatively analyzed the contributions for high near-infrared absorption film with high transparency. After determining the effects of internanoparticle distance within the layer on the STS, a novel double layer-coated film was fabricated with a small nanodistance between Cs0.33WO3 tungsten bronze nanoparticles. Considering the total solar energy spectrum, 380 W/m2 of solar absorption energy was estimated. Moreover, the double layer-coated film has 80% visible transmittance at 550 nm, 10% near-infrared transmittance at 1,000 nm, and low haze with 1% or less. In addition, the STS of the film was 0.793, and thus, the double layer-coated film was found to have excellent near-infrared absorption compared with that of a composite layer-coated film (0.696).