Transparent barrier coatings for flexible organic light-emitting diode applications

Silicon oxide (SiOx) and silicon nitride (SiNx) thin films have been deposited onto flexible polycarbonate (PC) substrates using plasma-enhanced (PE)CVD for transparent barrier applications. Comparing the internal stress, optical transparency, surface roughness, and impermeability results, a multilayer composed of parylene/SiOx/SiN(x center dot center dot center dot)parylene/SiOx/SiNx (PON...PON) is deposited on PC substrates and the optimum thicknesses of the SiNx, SiOx, and parylene layers is determined. Under optimum conditions, the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of SiOx(50 nm)/SiNx(50 nm) barrier coatings on PC at 80 degrees C decreases to values near 0.01 g m(-2) per day and 0.1 cm(3) m(-2) per day, respectively. To further reduce the WVTR and OTR values, parylene layers are used as a smoothing, defect-decoupling, and protective medium in the multilayer. It has been found that organic light-emitting diodes capped with double PON layers show no dark spots and exhibit better emissions than single PON layers after 100 h at 25 degrees C, and 40% relative humidity.