Efficient top-emitting organic light-emitting diodes with Sm/Ag bilayer cathode

A bilayer is used as a semitransparent cathode for top-emitting organic light emitting devices (top-emitting OLEDs). The bilayer cathode consists of samarium (Sm) and silver (Ag). Top-emitting OLEDs with the bilayer cathode showed enhanced current injection and high electroluminescence efficiency as compared with a Sm cathode. The maximum current efficiency of the top-emitting OLEDs with a Sm/Ag cathode is 9.9 cd/A, much greater than 4.9 cd/A obtained from the top-emitting OLEDs with a Sm cathode. The improved performance can be attributed to the balance between optical transparency and electrical conductivity of the Sm/Ag cathode.