Browsing by Author "Liu, Tswen-Hsin"

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Lithium manganese oxide as an effective buffer layer between organic and metal layers in organic light-emitting devices
(2006-09-04)
Liu, Tswen-Hsin
;
光電工程學系
;
Department of Photonics
Tris(8-hydroxyquinolinato)aluminum (Alq(3))-based organic light-emitting devices using a thermally deposited lithium manganese oxide layer between aluminum (Al) cathode and Alq(3) have been fabricated. The highest luminance efficiency obtained with a 1-nm-thick LiMnxOy layer is very similar to that of the device with 1-nm-thick LiF. However, the device with an 18 nm LiMnxOy layer obtained a longer operational stability although the luminance efficiency is lower. The improvements are attributed to lithium extractions of the lithium manganese oxide layer and the interfacial properties between Alq(3) and Al are discussed. (c) 2006 American Institute of Physics.
Organic light-emitting devices based on a highly robust osmium(II) complex
(2006-11-01)
Liu, Tswen-Hsin
;
Chen, Chin H.
;
光電工程學系
;
Department of Photonics
An osmium(II) complex, Os(fptz)(2)(PPh2Me)(2) [fptz=3-trifluoromethyl-5-(2-pyridyl)-1,2,4-triazole, PPh2Me=methyl-diphenyl-phosphan], when doped in a 4,4(')-N,N-'-dicarbazolebiphenyl host as a phosphorescent red emitter in organic light-emitting devices, has the unusual property of resisting concentration quenching and sustaining its external quantum efficiency (EQE) (8%-9%) over a wide range of doping concentration (20%-40%). Single-crystal x-ray diffraction evidence is presented that the difference in doping behaviors can be linked to the octahedral configuration of Os(fptz)(2)(PPh2Me)(2), which could prevent the undesirable molecular aggregation from occurring at high concentration, thus delaying the onset of quenching. Accordingly, the high doping concentration of Os(fptz)(2)(PPh2Me)(2) leads to a significant suppression of luminescence quenching at high brightness/current and achieves a "flat" EQE versus brightness response owing to the increase in the emission sites in the emission layer. (c) 2006 American Institute of Physics.