Browsing by Author "Lin, Kuan-Hung"

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Association structures of ionic liquid/DMSO mixtures studied by high-pressure infrared spectroscopy
(2011-01-28)
Jiang, Jyh-Chiang
;
Lin, Kuan-Hung
;
Li, Sz-Chi
;
Shih, Pao-Ming
;
Hung, Kai-Chan
Using high-pressure infrared methods, we have investigated close interactions of charge-enhanced C-H-O type in ionic liquid/dimethyl sulfoxide (DMSO) mixtures. The solvation and association of the 1-butyl-3-methylimidazolium tetrafluoroborate (BMI(+)BF(4)(-)) and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMM(+)BF(4)(-)) in DMSO-d(6) were examined by analysis of C-H spectral features. Based on our concentration-dependent results, the imidazolium C-H groups are more sensitive sites for C-H-O than the alkyl C-H groups and the dominant imidazolium C-H species in dilute ionic liquid/DMSO-d(6) should be assigned to the isolated (or dissociated) structures. As the dilute mixtures were compressed by high pressures, the loss in intensity of the bands attributed to the isolated structures was observed. In other words, high pressure can be used to perturb the association-dissociation equilibrium in the polar region. This result is remarkably different from what is revealed for the imidazolium C-H in the BMM(+)BF(4)(-)/D(2)O mixtures. DFT-calculations are in agreement with our experimental results indicating that C(4)-H-O and C(5)-H-O interactions seem to play non-negligible roles for BMM(+)BF(4)(-)/DMSO mixtures. (C) 2011 American Institute of Physics. [doi:10.1063/1.3526485]
Efficient and Color-saturated Inverted Bottom-emitting Organic Light-emitting Devices with a Semi-transparent Metal-assisted Electron Injection Layer
(2009)
Wu, Chang-Yen
;
Ho, Meng-Huan
;
Gao, Sin-Min
;
Su, Shang-Yu
;
Lin, Kuan-Hung
We report the development of highly efficient and color-saturated green fluorescent C545T dye-doped inverted bottom-emitting organic light emitting diode (IBOLED) by the insertion of a semi-transparent metal-assisted electron injection layer (SM-EIL) based on silver between the ITO and the n-doped electron injection layer (EIL). This n-i-p device with its synergistic microcavity effect achieved maximum efficiencies of 24 cd/A and 12.9 lm/ W and an external quantum efficiency of 6.2% with a saturated CIE(x,y) (0.24,0.71) which are twice better than those of the conventional OLED and over 60% improvement on IBOLED without the SM-EIL.
Efficient p-i-n Top-emitting Flexible Organic Light Emitting Diodes on Planarized Stainless Steel Foil
(2009)
Su, Shang-Yu
;
Ho, Meng-Huan
;
Kao, Pei-Yi
;
Wu, Chang-Yen
;
Peng, Yi-Hao
A high-efficiency p-i-n top-emitting flexible organic light emitting diode (TFOLED) employing highly reflective Ag as anode and semitransparent Ca/Ag as cathode was fabricated on SS substrate which was insulated and planarized with a specially formulated photoresist coating. By incorporating p-dopant (WO(3)) and a new n-dopant (PAK2) in hole and electron transparent layers, respectively, along with an optimized microcavity structure, a green fluorescent C545T doped Alq(3) TOLED on SS substrate achieved one of the highest efficiencies of 26.7 cd/A and 19.8 lm/W at 20 mA/cm(2) reported for flexible OLEDs.
Solvation and microscopic properties of ionic liquid/acetonitrile mixtures probed by high-pressure infrared spectroscopy
(2009-12-21)
Umebayashi, Yasuhiro
;
Jiang, Jyh-Chiang
;
Lin, Kuan-Hung
;
Shan, Yu-Lun
;
Fujii, Kenta
The microscopic features of binary mixtures formed by an ionic liquid (EMI(+)TFSA(-) or EMI(+)FSA(-)) and a molecular liquid (acetonitrile or methanol) have been investigated by high-pressure infrared spectroscopy. On the basis of its responses to changes in pressure and concentration, the imidazolium C-H appears to exist at least in two different forms, i.e., isolated and associated structures. The weak band at approximately 3102 cm(-1) should be assigned to the isolated structure. CD(3)CN can be added to change the structural organization of ionic liquids. The compression of an EMI(+)TFSA(-)/CD(3)CN mixture leads to the increase in the isolated C-H band intensity. Nevertheless, the loss in intensity of the isolated structures was observed for EMI(+)FSA(-)/CD(3)CN mixtures as the pressure was elevated. In other words, the associated configuration is favored with increasing pressure by debiting the isolated form for EMI(+)FSA(-)/CD(3)CN mixtures. The stronger C-H center dot F interactions in EMI(+)FSA(-) may be one of the reasons for the remarkable differences in the pressure-dependent results of EMI(+)TFSA(-) and EMI(+)FSA(-).
Structural change of ionic association in ionic liquid/water mixtures: A high-pressure infrared spectroscopic study
(2009-03-28)
Umebayashi, Yasuhiro
;
Jiang, Jyh-Chiang
;
Shan, Yu-Lun
;
Lin, Kuan-Hung
;
Fujii, Kenta
High-pressure infrared measurements were carried out to observe the microscopic structures of two imidazolium-based ionic liquids, i.e., 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide [EMI(+)(CF(3)SO(2))(2)N(-), EMI(+)TFSA(-)] and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide [EMI(+)(FSO(2))(2)N(-), EMI(+)FSA(-)]. The results obtained at ambient pressure indicate that the imidazolium C-H may exist in two different forms, i.e., isolated and network structures. As the sample of pure EMI(+)FSA(-) was compressed, the network configuration is favored with increasing pressure by debiting the isolated form. For EMI(+)TFSA(-)/H(2)O mixtures, the imidazolium C-H peaks split into four bands at high pressures. The new spectral features at approximately 3117 and 3190 cm(-1), being concentration sensitive, can be attributed to the interactions between the imidazolium C-H and water molecules. The alkyl C-H absorption exhibits a new band at approximately 3025 cm(-1) under high pressures. This observation suggests the formation of a certain water structure around the alkyl C-H groups. The O-H stretching absorption reveals two types of O-H species, i.e., free O-H and bonded O-H. For EMI(+)TFSA(-)/H(2)O mixtures, the compression leads to a loss of the free O-H band intensities, and pressure somehow stabilizes the bonded O-H configurations. The results also suggest the non-negligible roles of weak hydrogen bonds in the structure of ionic liquids.