Researchers from the University of Toronto developed the world's most efficient OLED on plastic, which they say is comparable with the best glass-based OLEDs. They discovered that coating the plastic substrate with a a 50-100 nano-meter thick layer of of tantalum(V) oxide (Ta2O5), an advanced optical thin-film coating material enabled them to re-construct the high-refractive index property previously limited to heavy metal-doped glass.