Characteristics of Light Emission Lifetime of Electroluminescent Phosphor Encapsulated by Titanium–Silicon–Oxide Film

Abstract

To improve the light emission lifetime of electroluminescent ZnS:Cu, Cl phosphor, the surface of the phosphor was coated with titanium–silicon–oxide (TSO) film that was deposited by chemical vapor deposition using a mixture of titanium tetrachloride (TiCl4) and silicon tetrachloride (SiCl4) vapors, and water vapor. By adding SiCl4 during the hydrolysis of TiCl4, the amount of Cl contained in the encapsulating film, which might induce the deterioration of the luminance of the phosphor, was reduced, and encapsulated phosphors with good luminescence characteristics, such as high luminance and long lifetime, were obtained. When the ratio of Si to Ti (Si/Ti) in the TSO film was 0.97, the phosphor encapsulated by the TSO film had the highest luminance and the longest lifetime; the initial luminance and the half-life of the luminance were 95.8 cd/m2 and 500 h or longer, respectively, when the encapsulated phosphor was operated at 40°C, 90% humidity, 100 V and 400 Hz. The luminescence lifetime of the encapsulated phosphors was approximately 25 times longer than that of nonencapsulated phosphors.