Analysis of metal-oxide-based charge generation layers used in stacked organic light-emitting diodes
نویسندگان
چکیده
We study electron and hole injection in MoO3 charge generation layers CGLs commonly used for establishing balanced injection in multilayer stacked organic light-emitting diodes SOLEDs . A compound CGL consisting of 100-Å-thick MoO3 and Li-doped 4,7-diphenyl-1,10-phenanthroline in a 1:1 molar ratio is demonstrated to have a high electron generation efficiency. Charge injection from the compound CGL is modeled based on a two-step process consisting of tunneling-assisted thermionic emission over an injection barrier of 1.2 0.2 eV and a trap level due to oxygen vacancies at 0.06 0.01 eV above the MoO3 valence band edge. Peak external quantum efficiencies EQEs of 10.5 0.2 %, 10.1 0.2 %, 8.6 0.2 %, and 8.9 0.2 % are obtained for trisphenylpyridine iridium-based electrophosphorescent OLEDs with indium tin oxide ITO anode/CGL cathode, CGL anode/CGL cathode, CGL anode/Al cathode, and ITO anode/Al cathode contacts, respectively. Based on our analysis, a three-element green emitting electrophosphorescent SOLED is demonstrated with a peak forward-viewing EQE= 24.3 1.0 % and a power efficiency of 19 1 lm /W. © 2010 American Institute of Physics. doi:10.1063/1.3275050
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Highly stable and high power efficiency tandem organic light-emitting diodes with transition metal oxide-based charge generation layers
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