Browsing by Author "Huang, Wei-Kai"

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Additional Refresh Technology (ART) of advanced-MVA(AMVA) mode for high quality LCDs
(2007)
Huang, Yi-Pai
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Huang, Wei-Kai
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Tsao, Cheng-Han
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Su, Jeng-Jia
;
Hou, Hong-Lung
We proposed "Additional Refresh Technology(ART)", which has the features of low color washout and fast response speed by only modifying the pixel layout. Besides, by utilizing ART technology, the image can be real time optimized with simple method. ART have succesfully been implemented as the Advanced-MV4 (AMVA) mode for AUO's LCD-TV products, that ART has become the promising solution of advanced LCD-TV panels for mass-production.
Advanced Technologies for High Quality LC Display
(2008)
Huang, Yi-Pai
;
Lin, Fang-Cheng
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Liao, Cheng-Yumr
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Hsu, Ya-Ting
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Huang, Wei-Kai
For achieving high quality LC displays, Advanced-MVA mode was proposed to wide the viewing angle, 4-color filed sequential method was utilized to increase the optical efficiency, and the local controlled LED backlight was applied to much improve the contrast and lower the power consumption.
Design and Characterization of Heteroleptic Ruthenium Complexes Containing Benzimidazole Ligands for Dye-Sensitized Solar Cells: The Effect of Fluorine Substituents on Photovoltaic Performance
(1970-01-01)
Huang, Wei-Kai
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Wu, Hui-Ping
;
Lin, Pi-Lun
;
Lee, Yuan-Pern
;
Diau, Eric Wei-Guang
"We designed heteroleptic ruthenium complexes (RD12-RD15) containing fluoro-substituted benzimidazole ligands for dye-sensitized solar cells (DSSCs). These dyes were synthesized according to a typical one-pot procedure with the corresponding ancillary ligands produced in two simple steps; they were prepared into DSSC devices according to the same conditions of fabrication. The eventual devices show a systematic trend of increasing V-OC and decreasing J(SC) with fluorine atoms of increasing number substituted on the ligand. The charge extraction results show that upward shifts of the TiO2 potential occurred when the fluoro-substituted dyes were sensitized on TiO2 with a systematic trend of shift N719 > RD15 (with 5 F) > RD12 (with 2 F) > RD5 (no F); the intensity modulated photovoltage spectra indicate that those fluoro substituents retard charge recombination with the electron lifetimes (tau(R)) in the order RD15 > RD12 > RD5 > N719, consistent with the variation of V-OC for the systems."
Design and Characterization of Heteroleptic Ruthenium Complexes Containing Benzimidazole Ligands for Dye-Sensitized Solar Cells: The Effect of Thiophene and Alkyl Substituents on Photovoltaic Performance
(2013-02-07)
Huang, Wei-Kai
;
Wu, Hui-Ping
;
Lin, Pi-Lun
;
Diau, Eric Wei-Guang
;
應用化學系
We designed heteroleptic ruthenium complexes RD16-RD18 containing fluoro-substituted and thiophene-based benzimidazole ligands for dye-sensitized solar cells. Whereas the substitution of only fluorine in the RD12 device has an effect of enhancing the open-circuit voltage (V-OC), additional substitution of thiophene in the RD16-RD18 sensitizers showed a slightly decreased V-OC. Systematic enhanced short-circuit current density (J(SC)) and efficiency (eta) of power conversion of the devices had the order RD18 > RD17 > RD16 > RD12 > N719, attributed to the increasing light-harvesting ability and the broadened spectral features with thiophene-based ligands. Measurements of charge extraction and intensity-modulated photovoltage spectra indicate that thiophene substitution shifts downward the TiO2 potential and accelerates charge recombination, but inclusion of a long hexyl chain on the thiophene moiety retards charge recombination to account for the variation of V-OC in the series. For a duration test of device performance at ambient temperature, only similar to 2% degradation of cell performance was found for the devices of RD18 and RD12 over 2000 h, but a 10% decrease in overall efficiency was observed in the N719 device.
Enhanced Light Harvesting with a Reflective Luminescent Down-Shifting Layer for Dye-Sensitized Solar Cells
(2013-06-26)
Hosseini, Zahra
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Huang, Wei-Kai
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Tsai, Cheng-Ming
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Chen, Teng-Ming
;
Taghavinia, Nima
For a dye-sensitized solar cell with a near-infrared squaraine (SQ1) sensitizer, the photovoltaic performance was enhanced remarkably with a reflective luminescent down-shifting (R-LDS) layer to increase the light-harvesting efficiency at the wavelength region 400-550 nm where the SQ1 dye has weak absorption. Relative enhancements greater than 200% in IPCE near 500 nm and 40-54% in J(SC) were achieved with red phosphor CaAlSiN3:Eu2+ as the LDS material, attaining 5.0 and 4.8% overall efficiencies of power conversion for the R-LDS layer coated on the counter electrode (front illumination) and working electrode (back illumination), respectively.
Femtosecond Infrared Transient Absorption Dynamics of Benzimidazole-Based Ruthenium Complexes on TiO2 Films for Dye-Sensitized Solar Cells
(2014-07-31)
Hsu, Hung-Yu
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Cheng, Chi-Wen
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Huang, Wei-Kai
;
Lee, Yuan-Pern
;
Diau, Eric Wei-Guang
By means of femtosecond infrared transient absorption spectra, we measured the interfacial electron-transfer dynamics for benzimidazole-based heteroleptic ruthenium dyes (RIDS, RD12, RD15-RD18) sensitized on TiO2 thin films. For all measurements, the first singlet metal-to-ligand charge-transfer states ((MLCT)-M-1) of the ruthenium complexes were excited at 519 nm and the injected electrons in the conduction band of TiO2 were probed at 4.3 mu m. All transient signals featured two rising components on a femtosecond-picosecond scale due to a two-step electron injection and an offset (N719, RD16-RD18) or a slow-decay (RD5, RD12, and RD15) component on a nanosecond microsecond scale due to a back electron transfer. A complicated two-step kinetic model was derived analytically to interpret the observed two rising components for which the rapid (tau(1) < 300 fs) and slow (tau(2) = 10-20 ps) electron injections arose from the singlet (MLCT)-M-1 and triplet (MLCT)-M-3 states, respectively. The amplitudes of the two electron-injection components (A(1) and A(2)) were controlled by the rate coefficient of the (MLCT)-M-1 --> (MLCT)-M-3 intersystem crossing; the variations of A(1) and A(2) are consistent with the trend of the corresponding Stokes shifts rationalized with a conventional energy-gap law for nonradiative transitions. Compared with the kinetics observed for the N719 dye, the involvement of a benzimidazole ligand in RD dyes had the effect of accelerating the two electron injections, thus improving the short circuit current of the device. RD dyes substituted with fluorine atoms and/or thiophene units in the benzirnidazole ligands showed a retardation of 3MLCT electron injection relative to that of the nonsubstituted RD5 dye. Acceleration of the BET process was observed for the RD5 dye (9 ns), and both fluoro-substituted dyes (14 ns for RD12 and 21 ns for RD15) and thiophene-substituted dyes (nonobservable for RD16-RD18) had significantly retarded BET kinetics. The observed kinetics of the (MLCT)-M-3 electron injection for all RD dyes is satisfactorily simulated with the Marcus theory.
Femtosecond Infrared Transient Absorption Dynamics of Benzimidazole-Based Ruthenium Complexes on TiO2 Films for Dye-Sensitized Solar Cells
(2014-07-31)
Hsu, Hung-Yu
;
Cheng, Chi-Wen
;
Huang, Wei-Kai
;
Lee, Yuan-Pern
;
Diau, Eric Wei-Guang
By means of femtosecond infrared transient absorption spectra, we measured the interfacial electron-transfer dynamics for benzimidazole-based heteroleptic ruthenium dyes (RIDS, RD12, RD15-RD18) sensitized on TiO2 thin films. For all measurements, the first singlet metal-to-ligand charge-transfer states ((MLCT)-M-1) of the ruthenium complexes were excited at 519 nm and the injected electrons in the conduction band of TiO2 were probed at 4.3 mu m. All transient signals featured two rising components on a femtosecond-picosecond scale due to a two-step electron injection and an offset (N719, RD16-RD18) or a slow-decay (RD5, RD12, and RD15) component on a nanosecond microsecond scale due to a back electron transfer. A complicated two-step kinetic model was derived analytically to interpret the observed two rising components for which the rapid (tau(1) < 300 fs) and slow (tau(2) = 10-20 ps) electron injections arose from the singlet (MLCT)-M-1 and triplet (MLCT)-M-3 states, respectively. The amplitudes of the two electron-injection components (A(1) and A(2)) were controlled by the rate coefficient of the (MLCT)-M-1 --> (MLCT)-M-3 intersystem crossing; the variations of A(1) and A(2) are consistent with the trend of the corresponding Stokes shifts rationalized with a conventional energy-gap law for nonradiative transitions. Compared with the kinetics observed for the N719 dye, the involvement of a benzimidazole ligand in RD dyes had the effect of accelerating the two electron injections, thus improving the short circuit current of the device. RD dyes substituted with fluorine atoms and/or thiophene units in the benzirnidazole ligands showed a retardation of 3MLCT electron injection relative to that of the nonsubstituted RD5 dye. Acceleration of the BET process was observed for the RD5 dye (9 ns), and both fluoro-substituted dyes (14 ns for RD12 and 21 ns for RD15) and thiophene-substituted dyes (nonobservable for RD16-RD18) had significantly retarded BET kinetics. The observed kinetics of the (MLCT)-M-3 electron injection for all RD dyes is satisfactorily simulated with the Marcus theory.
High-Performance Large-Scale Flexible Dye-Sensitized Solar Cells Based on Anodic TiO2 Nanotube Arrays
(2013-10-01)
Jen, Hsiu-Ping
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Lin, Meng-Hung
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Li, Lu-Lin
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Wu, Hui-Ping
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Huang, Wei-Kai
A simple strategy to fabricate flexible dye-sensitized solar cells involves the use of photoanodes based on TiO2 nanotube (TNT) arrays with rear illumination. The TNT films (tube length similar to 35 mu m) were produced via anodization, and sensitized with N719 dye for photovoltaic characterization. Pt counter electrodes of two types were used: a conventional FTO/glass substrate for a device of rigid type and an ITO/PEN substrate for a device of flexible type. These DSSC devices were fabricated into either a single-cell structure (active area 3.6 X 0.5 cm(2)) or a parallel module containing three single cells (total active area 5.4 cm(2)). The flexible devices exhibit remarkable performance with efficiencies eta = 5.40 % (single cell) and 4.77 % (parallel module) of power conversion, which outperformed their rigid counterparts with eta = 4.87 % (single cell) and 4.50 % (parallel model) under standard one-sun irradiation. The flexible device had a greater efficiency of conversion of incident photons to current and a broader spectral range than the rigid device; a thinner electrolyte layer for the flexible device than for the rigid device is a key factor to improve the light-harvesting ability for the TNT-DSSC device with rear illumination. Measurements of electrochemical impedance spectra show excellent catalytic activity and superior diffusion characteristics for the flexible device. This technique thus provides a new option to construct flexible photovoltaic devices with large-scale, light-weight, and cost-effective advantages for imminent applications in consumer electronics.
Hybrid Titania Photoanodes with a Nanostructured Multi-Layer Configuration for Highly Efficient Dye-Sensitized Solar Cells
(2013-05-02)
Wu, Hui-Ping
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Lan, Chi-Ming
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Hu, Jyun-Yu
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Huang, Wei-Kai
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Shiu, Jia-Wei
To construct a hybrid titania photoanode containing nanoparticles and nanorods of varied size in a multilayer (ML) configuration for dye-sensitized solar cells, the essence of our ML design is a bilayer system with additional layers of nanorods of well-controlled size inserted between the transparent and the scattering layers to enhance the light harvesting capability for photosensitizers with small absorptivity, such as Z907. We measured charge-extraction and intensity-modulated photoelectric spectra to show the advantages of one-dimensional nanorods with an improved electron-transport property and an upward shift of the potential band edge; a favorable ML configuration was constructed to have a cascade potential feature for feasible electron transport from long nanorods, to normal nanorods, to small nanoparticles. On the basis of the ML system reported herein, we demonstrate how the performance of a Z907 device is improved to attain eta similar to 10%, which is a milestone for its future commercialization.
Molecular engineering of cocktail co-sensitization for efficient panchromatic porphyrin-sensitized solar cells
(2012-12-01)
Wu, Hui-Ping
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Ou, Zih-Wei
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Pan, Tsung-Yu
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Lan, Chi-Ming
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Huang, Wei-Kai
Co-sensitization of two or more dyes with complementary absorption spectra on a semiconductor film is an effective approach to enhance the performance of a dye-sensitized solar cell (DSSC). Porphyrin sensitizer YD2-oC8 showed outstanding photovoltaic performance co-sensitized with an organic dye to cover the entire visible spectral region, 400-700 nm. To promote the light-harvesting capability beyond 700 nm, a porphyrin dimer (YDD6) was synthesized for a co-sensitized system. We report a systematic approach for engineering of molecular co-sensitization of TiO2 films in a cocktail solution containing YD2-oC8, an organic dye (CD4) and YDD6 in a specific molar ratio to optimize the photovoltaic performance of the device. The resulting device showed panchromatic spectral features in the IPCE action spectrum in the region 400-700 nm attaining efficiencies of 75-80%; the spectrum is extended to the near-IR region attaining 40-45% in 700-800 nm region, giving J(SC)/mA cm(-2) = 19.28, V-OC/mV = 753, FF = 0.719, and eta = 10.4% under standard AM 1.5 G one-sun irradiation. This performance is superior to what is obtained from the individual single-dye devices and the two-dye co-sensitized systems. The shifts of TiO2 potential upon dye uptake and the kinetics of charge recombination were examined through measurements of the charge extraction (CE) and intensity-modulated photovoltage spectroscopy (IMVS), respectively. Five co-sensitized systems were investigated to demonstrate that suppression of dye aggregation of YDD6 in the co-sensitized film is a key factor to further improve the device performance.
Relaxation Dynamics and Structural Characterization of Organic Nanobelts with Aggregation-Induced Emission
(1970-01-01)
Chang, Chih-Wei
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Bhongale, Chetan Jagdish
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Lee, Chi-Shen
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Huang, Wei-Kai
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Hsu, Chain-Shu
"We prepared the fluorescent nanobelts of cyano-substituted 1,4-distyrylbenzene derivative (CNDSB) with the reprecipitation method. CNDSB is nonemissive in solution but with strong aggregation-induced emission (AIE) in belt-like structure. The molecular structure predicted by quantum chemical calculations indicates a twisted conformation of CNDSB monomer, while the solid-state X-ray structure of the CNDSB crystal features herringbone-type arrangement and three benzene rings arrange in nearly planar conformation. Femto- and picosecond time-resolved fluorescence spectroscopy are implemented to study the photophysics and the origin of the ME effect in CNDSB nanobelts. The fluorescence quenching of CNDSB in THF solution arises from the efficient nonradiative isomerization channel. In this study, the fluorescence decay of CNDSB embedded in poly(methyl methacrylate) matrix is slowed down due to the restriction of intra:molecular motions in the solid matrix. In nanobelt structure, the fluorescence lifetime further increases due to the intermolecular interaction between H-type aggregates. Both the steady-state and time-resolved studies suggests that there are at least two different packing structures might exist in nanobelts, and the relative composition of these two different structures gradually changes in different sizes of nanobelts."
Size-Controlled Anatase Titania Single Crystals with Octahedron-like Morphology for Dye-Sensitized Solar Cells
(2012-12-01)
Shiu, Jia-Wei
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Lan, Chi-Ming
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Chang, Yu-Cheng
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Wu, Hui-Ping
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Huang, Wei-Kai
A simple hydrothermal method with titanium tetra-isopropoxide (TTIP) as a precursor and triethanolamine (TEOA) as a chelating agent enabled growth in the presence of a base (diethylamine, DEA) of anatase titania nanocrystals (HD1-HD5) of controlled size. DEA played a key role to expedite this growth, for which a biphasic crystal growth mechanism is proposed. The produced single crystals of titania show octahedron-like morphology with sizes in a broad range of 30-400 nm; a typical, extra large, octahedral single crystal (HD5) of length 410 nm and width 260 nm was obtained after repeating a sequential hydrothermal treatment using 1103 and then 1104 as a seed crystal. The nanocrystals of size similar to 30 nm (HD1) and similar to 300 nm (HD5) served as active layer and scattering layer, respectively, to fabricate N719-sensitized solar cells. These HD devices showed greater V-oc than devices of conventional nanoparticle (NP) type; the overall device performance of HD attained an efficiency of 10.2% power conversion at a total film thickness of 28 mu m, which is superior to that of a NP-based reference device (eta = 9.6%) optimized at a total film thickness of 18-20 mu m. According to results obtained from transient photoelectric and charge extraction measurements, this superior performance of HD devices relative to their NP counterparts is due to the more rapid electron transport and greater TiO2 potential.
Spirally configured cis-stilbene/fluorene hybrids as bipolar, organic sensitizers for solar cell applications
(2012)
Chao, Wei-Shan
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Liao, Ken-Hsien
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Chen, Chien-Tien
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Huang, Wei-Kai
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Lan, Chi-Ming
Hybrids based on a dibenzosuberene core bearing a spiro-fluorene junction at the C-5 position and with amino donor and beta-thiophenyl-alpha-cyanoacrylic acid acceptor groups at C-3 and C-7, respectively, serve as new organic sensitizer materials for solar cell applications. Solar cell devices based on these materials show a conversion efficiency (eta) of up to 6.1% (V-oc = 697 mV, J(sc) = 12.2 mA cm(-2), FF = 0.72) under AM 1.5 G conditions. The best IPCE values exceed 75% within the 450-550 nm absorption range.
Synthesis and characterization of diporphyrin sensitizers for dye-sensitized solar cells
(2010)
Mai, Chi-Lun
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Huang, Wei-Kai
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Lu, Hsueh-Pei
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Lee, Cheng-Wei
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Chiu, Chien-Lan
Novel porphyrin dimers with broad and strong absorption in the visible and/or near IR regions have been synthesized; the meso-meso-linked porphyrin dimer (YDD1) exhibited the best photovoltaic performance with power conversion efficiency 5.2% under AM 1.5G one solar illumination.
Synthesis and Characterization of Novel Heteroleptic Ruthenium Complexes for Dye-Sensitized Solar Cells
(2010-10-01)
Huang, Wei-Kai
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Lan, Chi-Ming
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Liu, Yu-Sin
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Lee, Pei-Heng
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Chang, Shu-Mei
We report three novel heteroleptic ruthenium complexes, RD1: Ru[(dcbpy)(1-methyl-2-(pyridin2-yl)-1 H-benzimidazole)(NCS)(2), RD2: Ru [(dcbpy) (2-(pyridine-2-yl) benzothiazole) (NCS)(2), and RD3: Ru[(dcbpy)(2-(pyridin-2-yl) benzoxazole) (NCS)2, for dye-sensitized solar cell applications. We found that RD1 exhibits a dye loading amount two times higher than that of N719, which gives a broad IPCE action spectrum for the spectral response beyond 800 nm. This series of dyes can be easily synthesized in three steps with the best dye (RD1) reaching 80% cell performance of N719.
Synthesis and electron-transfer properties of benzimidazole-functionalized ruthenium complexes for highly efficient dye-sensitized solar cells
(2010)
Huang, Wei-Kai
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Cheng, Chi-Wen
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Chang, Shu-Mei
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Lee, Yuan-Pern
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Diau, Eric Wei-Guang
Novel heteroleptic ruthenium complexes-RD1, RD5, RD10 and RD11-with ligands based on benzimidazole were synthesized and characterized for application to dye-sensitized solar cells (DSSC); the remarkable performance of RD5-based DSSC is understood for its superior light-harvesting ability and slower charge-recombination kinetics.
Synthesis of push-pull porphyrin dyes with dimethylaminonaphthalene electron-donating groups and their application to dye-sensitized solar cells
(2016-01-01)
Adineh, Maryam
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Tahay, Pooya
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Huang, Wei-Kai
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Wu, Hui-Ping
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Diau, Eric Wei-Guang
Two new donor-pi-bridge-acceptor zinc porphyrins with dimethylaminonaphthalene electron donating moieties, coded T1 and T2, were synthesized and used as sensitizers in dye sensitized solar cells (DSSCs). Both dyes showed excellent photovoltaic properties with power conversion efficiencies of 8.0 and 9.6% for T1 and T2 respectively, forwhich the device performance of T2 dye is superior to that of N719 dye.