Amorphous oxide based microcavity color filter with high selectivity

Amorphous oxide based thin film visible light color filters have been fabricated by using a microcavity structure with amorphous silicon-zinc-tin-oxide (a-SZTO) and silver (Ag) multilayer. Metal-oxide-metal microcavity structure adopted transparent amorphous oxide materials because their high refractive index (n) values (higher than 2) and amorphous phase which does not include grain boundary are useful to obtain highly selective color filtering characteristics with high transparency as well as simple fabrication process and reliable reproducibility. The refractive index (n) values and extinction coefficient(k) values of a-SZTO were extracted by using ellipsometry. The simulation program was used to design to optimize color filter at each wavelength. The color filter was fabricated by changing the thickness of the middle a-SZTO layer at fixed thickness of upper and bottom Ag layer. As the thickness of the middle a-SZTO layer increased, the wavelength shifted in the direction of longer wavelength, and filtered visible color is varied from blue to red. The amorphous oxide based color filter showed high transmittance of over 60% mainly due to amorphous phase of a-SZTO and each color filters for red, green and blue exhibited highly selective visible light filtering characteristics with narrow full-width at half maximum of less than 30 nm mainly due to high refractive index of a-SZTO. The electrical characteristics were measured by using Hall measurement system, with a very low resistivity of about ~10⁻⁵ Ω cm. These results can be directly applied to the electrode materials of the organic solar cell and the color electrode for photovoltaics.