Characteristics of transparent SiN_x thin-film passivation layer grown by CECVD for top-emitting OLEDs

The characteristics of a SiNx passivation layer grown by a specially designed catalyzer-enhanced chemical vapor deposition (CECVD) system for top-emitting organic light-emitting diodes (TOLEDs) were investigated. Using a tungsten catalyzer connected in series, a high-density SiNx passivation layer with high transmittance was deposited on TOLEDs at a substrate temperature of 50°C. Even at low substrate temperature, 150 nm thick SiNx passivation layer prepared by CECVD exhibited a low water vapor transmission rate of 2- 6× 10-2 g m2 day. In addition, it was found that the transmittance of SiNx film at 550 nm was significantly influenced by the hydrogen flow rate. Current density-voltage-luminescence results of TOLEDs passivated with a 150 nm thick SiNx film indicated that the electrical and optical properties of TOLEDs were not affected by the high temperature tungsten catalyzer during the SiNx deposition. The lifetime to half initial luminance of a TOLED passivated with a 150 nm thick SiNx layer was much longer than that of a nonpassivated reference sample. This shows that the CECVD is a promising plasma free thin-film passivation technique for high-performance TOLEDs and flexible displays.