A lightweight, flexible, plastic substrate is coated with at least one layer, such that the substrate has desired barrier and electrode characteristics useful in constructing OLED displays. The layer has both a low enough resistance to function as an electrode for the display, and low oxygen and moisture permeability. The display is thereby protected from oxygen and moisture degradation. For lower permeability and/or higher conductivity, multiple alternating layers of barrier materials and conductive materials may be applied. The barrier material includes at least one of a thin metallic film, an organic polymer, a thin transparent dielectric, a thin transparent metal nitride, and a thin transparent conductive oxide. The conductive material includes at least one of a thin transparent conductive oxide, a thin transparent metallic film, and a thin transparent metal nitride. Preferably, a multilayer polymer base coat is deposited over the substrate to exclude moisture and atmospheric gases.