Browsing by Author "Horng, S. F."

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Electron transport and electroluminescent efficiency of conjugated polymers
(2009-01-01)
Tseng, S. R.
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Chen, Y. S.
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Meng, H. F.
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Lai, H. C.
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Yeh, C. H.
The relation between charge balance and electroluminescent efficiency for polymers is studied systematically in this work. Light-emitting diodes of several kinds of polymers with very different efficiency are compared. The electron and hole currents are measured in the uni-polar devices and fitted by the theoretical model to get carrier mobilities. The universal features of the high efficiency polymers are that the electron and hole mobilities are comparable and the electron current is larger than the hole current due to the higher hole barriers. The electron current is more crucial than hole current to determine the efficiency in the bipolar light-emitting diode. The purity of polymers and low electron injection barriers both play significant roles in producing stronger electron currents. These results give the physical rules for designing new polymers and the device structures to achieve highly electroluminescent devices. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.
Triplet exciton energy transfer in polyfluorene doped with heavy metal complexes studied using photoluminescence and photoinduced absorption
(2006-12-01)
Liao, H. H.
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Meng, H. F.
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Horng, S. F.
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Lee, W. S.
;
Yang, J. M.
Modulated photoinduced absorption and photoluminescence are used to study triplet-to-triplet Dexter energy transfer in Ir-complexes/polyfluorene blend systems. There is no Dexter energy transfer for red iridium (III)bis[2-(9,9-dibutylfluorenyl)-1-isoquinoline(acetylacetonate)] (DFIr) and red iridium (III) bis([2-(2-benzo-thienyl)pyridinatoN,C3] acetyl-acetonate) (BtpIr) dopants. Although green iridium(III)tris[2-(4-tolyl)pyridinato-N,C2] [Ir(mppy)(3)] has no triplet confinement in polyfluorene host, it has clear evidence for Dexter energy transfer. Aggregation and dopant lifetime are shown to significantly affect the energy transfer. The presence of Dexter transfer implies the possibility to harvest triplet excitons of polyfluorene in polymer light-emitting diodes even without carrier trapping and triplet exciton confinement.
Unipolar Switching Behaviors of RTO WO(X) RRAM
(2010-02-01)
Chien, W. C.
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Chen, Y. C.
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Lai, E. K.
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Yao, Y. D.
;
Lin, P.
The microstructure and electrical properties of the WO(X)-based resistive random access memory are investigated in this letter. The WO(X) layer is formed by converting the surface of the W plug with a CMOS-compatible rapid thermal oxidation process. The conductive-atomic-force-microscopy result indicates that nanoscale conducting channels exist in the WO(X) layer and result in a low initial resistance. This letter studies the unipolar operation-the programming, reading, and reliability behaviors of the device are characterized systematically. The low programming voltages for RESET (3.3 V/50 ns) and fast SET speed (3 V/300 ns) are achieved along with cycling endurance greater than 10(7) times. In addition, the device is immune to read disturb. A 2-bit/cell operation is also demonstrated for high-density applications.
Unipolar Switching Behaviors of RTO WOX RRAM
(2010-02-01)
Chien, W. C.
;
Chen, Y. C.
;
Lai, E. K.
;
Yao, Y. D.
;
Lin, P.
The microstructure and electrical properties of the WOX-based resistive random access memory are investigated in this letter. The WOX layer is formed by converting the surface of the W plug with a CMOS-compatible rapid thermal oxidation process. The conductive-atomic-force-microscopy result indicates that nanoscale conducting channels exist in the WOX layer and result in a low initial resistance. This letter studies the unipolar operation-the programming, reading, and reliability behaviors of the device are characterized systematically. The low programming voltages for RESET (3.3 V/50 ns) and fast SET speed (3 V/300 ns) are achieved along with cycling endurance greater than 10(7) times. In addition, the device is immune to read disturb. A 2-bit/cell operation is also demonstrated for high-density applications.