In this study, the characteristics of functional films were investigated according to the number of coatings and their heat treatment times. The functional coating films were deposited on glass substrates made of the same material as the cover glass of photovoltaic (PV) modules. Each film was coated once by brushing with a special silica-based solution, and each heat treatment was done using a hot-air fan for 2 min at 300 °C. The substrates were coated once, twice, and thrice, respectively, and were annealed once, twice, and thrice by drying and cooling alternately. The specimens were then analyzed for their anti-pollution properties, contact angles, light transmittance, and mechanical properties. The anti-pollution function was confirmed through a self-cleaning test, while the contact angle and light transmittance were examined using special equipment. Mechanical properties, including hardness and adhesion, were confirmed using the standard hardness testing method (ASTM D3363) such as those using an H-9H, F, HB, or B-6B pencil (Mitsubishi, Japan) and a standard adhesion testing method (ASTM D3359). It was confirmed that the film coated once yielded a very low contact angle of 8.9° and very good anti-pollution properties. Its adhesion and strength also showed high values of 5B and 9H, respectively.

Building-integrated photovoltaics (BIPV) extend the traditional role of buildings by enabling on-site power generation while simultaneously addressing architectural and aesthetic requirements. In this context, colored glass is no longer a purely decorative element but a functional component that directly influences optical transmittance, color perception, and electrical performance. Despite increasing interest in colored BIPV modules, systematic quantitative analyses of color dispersion and optical property variation within the same color family remain limited. In this study, colored glass for BIPV applications was fabricated by depositing thin films with thicknesses below 100 nm onto indium tin oxide (ITO)-coated glass substrates using radio-frequency (R.F.) magnetron sputtering with various metal targets, including MoO₃, WO₃, Si, TiN, and SiO₂. The fabricated specimens were categorized into red, yellow, and blue color families and systematically analyzed in terms of optical transmittance, sheet resistance, and quantitative colorimetric properties. Color characteristics were evaluated using CIELAB coordinates (L*, a*, b*) and CIE 1931 chromaticity coordinates (x, y), while color differences (ΔE*ab) were calculated relative to a MoO₃/WO₃ reference specimen. The chromaticity distributions revealed continuous and material-dependent color-shift trajectories within the CIE 1931 color space rather than random dispersion. Oxide-based coatings exhibited gradual shifts toward the yellow region with relatively high lightness, whereas TiN-based coatings showed distinct migration toward the blue region accompanied by reduced lightness. These color shifts were consistently correlated with changes in spectral transmittance and electrical resistance induced by variations in sputtering targets and deposition conditions. The results demonstrate that color variation in sputter-deposited BIPV glass arises from systematic optical responses across the visible spectrum rather than from isolated wavelength-selective absorption. This study provides a quantitative framework for comparing color realization characteristics within the same color family and offers practical guidance for material selection and process optimization in the design of colored glass for BIPV applications.

Building-integrated photovoltaics (BIPV) require front-glass materials that satisfy both aesthetic and functional requirements. In this study, colored glass for BIPV applications was fabricated on indium tin oxide (ITO)-coated glass substrates using Radio-Frequency (RF) magnetron sputtering with various ceramic targets, including metal oxides (MoO₃, WO₃, and SiO₂), a nitride (TiN), and Si. The fabricated samples were classified into red, yellow, and blue color families and evaluated in terms of optical transmittance, sheet resistance, and colorimetric properties. The color characteristics were quantitatively analyzed using CIELAB coordinates (L^*, a^*, and b^*) and CIE 1931 chromaticity coordinates (x, y). The results showed that the chromaticity distributions followed continuous material-dependent trajectories rather than random dispersion. Oxide-based coatings generally shifted toward the yellow region with relatively high lightness, whereas TiN-based coatings shifted toward the blue region with reduced lightness. In addition, transmittance analysis in the photovoltaic-relevant spectral range indicated that Si-based coatings exhibited relatively high optical transparency. The observed color variations are consistent with thin-film interference and the optical properties of the coating materials. This study focuses on the comparative evaluation of optical, electrical, and colorimetric characteristics. This study provides a comparative framework for color realization analysis and offers practical guidance for material selection in colored BIPV glass design.