Transparent organic light-emitting devices with LiF/Yb:Ag cathode

Highly transparent organic light-emitting devices (TOLEDs) based on LiF/Yb:Ag cathode are reported. The device with a structure of Indium tin oxide/N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biph-enyl-4, 4′-diamine (50 nm)/tris (8-hydroxyquinoline) aluminum (50 nm)/LiF(0.5 nm)/Yb:Ag (15 nm, volume ratio 1:1) shows about the same luminances and spectra from both sides. At a current density of 20 mA/cm², the luminance and electroluminescent efficiency of the top/bottom side are 165/167 cd/m² and 0.825/0.835 cd/A, respectively. We attribute the characteristics to the high transmittance and low reflectivity of Yb:Ag cathode. The results suggest that LiF/Yb:Ag electrode can be used as an effective and stable cathode in TOLEDs or top-emitting OLEDs.