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Thin‐film encapsulated white organic light top‐emitting diodes using a WO 3 /Ag/WO 3 cathode to enhance light out‐coupling
Author(s) -
Bouzid Karim,
Maindron Tony,
Kanaan Hani
Publication year - 2016
Publication title -
journal of the society for information display
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 52
eISSN - 1938-3657
pISSN - 1071-0922
DOI - 10.1002/jsid.466
Subject(s) - cathode , oled , materials science , luminance , optoelectronics , diode , work function , layer (electronics) , luminous efficacy , light emitting diode , light emission , optics , nanotechnology , chemistry , physics
An alternative design of a semitransparent cathode for top‐emission white‐fluorescent organic light‐emitting diodes (OLEDs) has been investigated. The scope of this study was to improve the luminance of OLEDs used for displays while keeping the current density versus voltage characteristic unchanged for addressing purposes. The use of an optical simulation tool allowed the optimization of the tri‐layer cathode WO 3 /Ag/WO 3 to increase the light out‐coupling coefficient of the device leading to an increased white emission compared with a reference device with a Ca/Ag cathode. An increase of ~40% in luminance has been calculated by simulation and experimentally confirmed. The p‐i‐n OLED structure underneath the tri‐layer cathode allowed an efficient injection of electrons independently from the work function of WO 3 . The WO 3 /Ag/WO 3 cathode has been also confirmed to be compatible with the atomic layer deposition technique for thin film encapsulation. Finally, lifetime measurements up to 600 h have been carried out to quantify the enhancements induced by the new cathode compared with the control device. It has been found that lifetimes of both cathode architectures are similar on this time scale, while the WO 3 /Ag/WO 3 cathode shows a lower voltage drift versus aging.