Open AccessTransparent organic light-emitting devices with LiF/Mg:Ag cathode
Author(s) -
B. J. Chen,
Xiao Wei Sun,
Say Hwa Tan
Publication year - 2005
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/opex.13.000937
Subject(s) - cathode , materials science , indium tin oxide , optoelectronics , anode , current density , optics , refractive index , electroluminescence , layer (electronics) , electrode , nanotechnology , chemistry , physics , quantum mechanics
Transparent organic light-emitting devices (TOLED) based on a stacked transparent cathode of a LiF/Mg:Ag were investigated. The device has a structure of indium-tin-oxide (ITO)/ N, N'-diphenyl-N, N'-(3- methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) (90 nm)/ tris-(8- hydroxyquinoline) aluminum (Alq3) (80 nm)/LiF (0.5 nm)/Mg:Ag (20 nm)/Alq3 (50 nm), where the transparent capping layer of 50 nm Alq3 acts as refractive index matching layer to optimize optical output. The turn-on voltage of the device is as low as 2.8 V. The device also shows high optical transparency and low reflectivity in the visible region, approximately 40% of light can emit from the top cathode side and 60% of the light from bottom ITO glass. At injection current density of 20 mA/cm2, the current efficiency, for bottom emission from ITO anode side and top emission from metal cathode side, is 3.4 cd/A and 2.2 cd/A, respectively. The lower turnon voltage and higher efficiency of device are due to enhancing electron injection by using LiF/Mg:Ag cathode.