Browsing by Author "Lee, Kun-Mu"

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Dye-sensitized solar cells with a micro-porous TiO(2) electrode and gel polymer electrolytes prepared by in situ cross-link reaction
(2009-11-01)
Lee, Kun-Mu
;
Hsu, Chih-Yu
;
Chiu, Wei-Hao
;
Tsui, Meng-Chin
;
Tung, Yung-Liang
The ionic conductivities and performances of dye-sensitized solar cells(DSSCs) of gel polymer electrolytes(GPEs) prepared by in situ cross-link reaction with different cross-linkers were investigated. The poly(imidazole-co-butylmethacrylate)-based GPE containing the 1,2,4,5-tetrakis(bromomethyl)benzene (B4Br) cross-linker showed a higher ionic conductivity than that containing cross-linkers with a linear structure, due to the formation of micro-phase separation that resulted in an increase in ion transport paths in the GPE. Moreover, the co-adsorbent((4-pyridylthio) acetic acid, PAA) co-adsorbed with N3 dye on the TiO(2) electrode not only reduced dye aggregation, but also reacted with the cross linkers in the GPE at the TiO(2)/GPE interface. A decrease in the charge transport resistance at the TiO2/GPE interface was noted after forming the gel; thus the value of J(SC) significantly increased from 7.72 to 10.00 m A cm(-2). In addition, in order to reduce the ionic diffusion resistance within the TiO(2) electrode, incorporation of monodispersed PMMA in the TiO(2) paste was considered. With the optimal weight ratio of PMMA/TiO(2) (w/w 3.75), the TiO(2) electrode exhibited larger pores (ca. 350 nm) uniformly distributed afters intering at 500 degrees C, and the ionic diffusion resistance within the TiO2 film could significantly be reduced. The cell conversion efficiency increased from 3.61% to 5.81% under illumination of 100 mW cm (-2), an improvement of ca. 55%. (C) 2009 Elsevier B. V. All rights reserved.
Dye-sensitized solar cells with a micro-porous TiO2 electrode and gel polymer electrolytes prepared by in situ cross-link reaction
(2009-11-01)
Lee, Kun-Mu
;
Hsu, Chih-Yu
;
Chiu, Wei-Hao
;
Tsui, Meng-Chin
;
Tung, Yung-Liang
The ionic conductivities and performances of dye-sensitized solar cells(DSSCs) of gel polymer electrolytes(GPEs) prepared by in situ cross-link reaction with different cross-linkers were investigated. The poly(imidazole-co-butylmethacrylate)-based GPE containing the 1,2,4,5-tetrakis(bromomethyl)benzene (B4Br) cross-linker showed a higher ionic conductivity than that containing cross-linkers with a linear structure, due to the formation of micro-phase separation that resulted in an increase in ion transport paths in the GPE. Moreover, the co-adsorbent((4-pyridylthio) acetic acid, PAA) co-adsorbed with N3 dye on the TiO2 electrode not only reduced dye aggregation, but also reacted with the cross linkers in the GPE at the TiO2/GPE interface. A decrease in the charge transport resistance at the TiO2/GPE interface was noted after forming the gel; thus the value of J(SC) significantly increased from 7.72 to 10.00 m A cm(-2). In addition, in order to reduce the ionic diffusion resistance within the TiO2 electrode, incorporation of monodispersed PMMA in the TiO2 paste was considered. With the optimal weight ratio of PMMA/TiO2 (w/w 3.75), the TiO2 electrode exhibited larger pores (ca. 350 nm) uniformly distributed afters intering at 500 degrees C, and the ionic diffusion resistance within the TiO2 film could significantly be reduced. The cell conversion efficiency increased from 3.61% to 5.81% under illumination of 100 mW cm (-2), an improvement of ca. 55%. (C) 2009 Elsevier B. V. All rights reserved.
Effects of mesoscopic poly (3,4-ethylenedioxythiophene) films as counter electrodes for dye-sensitized solar cells
(2010-01-01)
Lee, Kun-Mu
;
Chiu, Wei-Hao
;
Wei, Hung-Yu
;
Hu, Chih-Wei
;
Suryanarayanan, Vembu
Counter electrode coated with chemically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) in a dye-sensitized solar cell (DSSC) was studied. The surface morphology and the nature of I(-)/I(3)(-) redox reaction based on PEDOT film were investigated using Atomic Force Microscopy and Cyclic Voltammetry, respectively. The performance of the DSSCs containing the PEDOT coated electrode was compared with sputtered-Pt electrode. We found that the root mean square roughness decreases and conductivity increases as the molar ratio of imidazole (Im)/EDOT in the PEDOT film increases. The DSSC containing the PEDOT coated on fluorine doped tin oxide glass with Im/EDOT molar ratio of 2.0, showed a conversion efficiency of 7.44% compared to that with sputtered-Pt electrode (7.77%). The high photocurrents were attributed to the large effective Surface area of the electrode material resulting in good catalytic properties for T(3) reduction. Therefore, the incorporation of a multi-walled carbon nanotube (MWCNT) in the PEDOT film, coated on various substrates was also investigated. The DSSC containing the PEDOT films with 0.6 wt.% of MWCNT on stainless steel as counter electrode had the best cell performance of 8.08% with short-circuit current density, open-circuit voltage and fill factor of 17.00 mA cm(-2), 720 mV and 0.66, respectively. (C) 2009 Elsevier B.V. All rights reserved.
High efficiency flexible dye-sensitized solar cells by multiple electrophoretic depositions
(2011-04-01)
Chiu, Wei-Hao
;
Lee, Kun-Mu
;
Hsieh, Wen-Feng
;
光電工程學系
;
Department of Photonics
A multiple electrophoretic deposition (EPD) of binder-free TiO(2) photoanode has been developed to successfully fill the crack occurring after air-drying on the first EPD-TiO(2) film surface. With the slow 2nd EPD, high quality TiO(2) thin films are acquired on flexible ITO/PEN substrates at room temperature and the device efficiency of the dye-sensitized solar cell achieved 5.54% with a high fill factor of 0.721. Electrochemical impedance spectroscopy measurements analyze the great enhancement of the photovoltaic performance through multiple EPD. The electron diffusion coefficient improved by about 1 order of magnitude in crack-less multiple-EPD TiO(2) films. With the scattering layer, the device reveals a high conversion efficiency of up to 6.63% under AM 1.5 G one sun irradiation, having a short circuit current density, open circuit voltage, and filling factor of 12.06 mA cm(-2), 0.763 V and 0.72, respectively. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
Improved performance of flexible dye-sensitized solar cells by introducing an interfacial layer on Ti substrates
(2011)
Lee, Chia-Hua
;
Chiu, Wei-Hao
;
Lee, Kun-Mu
;
Hsieh, Wen-Feng
;
Wu, Jenn-Ming
The recombination reaction of injected electrons with triiodide ion in the electrolyte limits the efficiency of dye-sensitized solar cells (DSSCs). This study reports the preparation of a sponge-like and conformal TiO(2) underlayer by hydrogen peroxide oxidation of Ti foil. This underlayer serves as a charge recombination barrier layer at the nanocrystalline TiO(2)/substrate interface, and suppresses the recombination reaction. This sponge-like TiO(2) underlayer increases the electrical contact area between the Ti substrate and nanocrystalline TiO(2), helping nanocrystalline TiO(2) attach to the Ti substrate. This study compares the performance of DSSCs that were subjected to different Ti surface treatments. Electrochemical impedance spectroscopy results confirm that the proposed sponge-like TiO(2) underlayer increased the open-current voltage (V(OC)) and fill factor (FF) due to prolonged electron life time (tau(eff)), and minimized resistance at the TiO(2)/Ti interface (R(CT)). With an optimal thickness of nanocrystalline TiO(2) and concentration of I(2), we achieved a conversion efficiency of 6.75% for a back-illuminated DSSC.
Improvement on the long-term stability of flexible plastic dye-sensitized solar cells
(2011-10-15)
Lee, Kun-Mu
;
Chiu, Wei-Hao
;
Lu, Ming-De
;
Hsieh, Wen-Feng
;
光電工程學系
We investigate the long-term stability of performance for plastic dye-sensitized solar cells (DSSCs) based on organic iodides (TBAI or PMII) in methoxypropionitrile-based electrolytes. Plastic DSSCs containing TBAI maintain 96.9% of baseline efficiency under more than 1000 h prolonged one sun light irradiation and thermal stress (60 degrees C) aging. The factors of device long-term stability, such as the effects of organic iodides, cell-sealing conditions, and the sheet resistance of indium tin oxide coated polyethylene naphthalate substrate (ITO/PEN) are discussed via using electrochemical impedance spectroscopy and electrical resistance measurement. (C) 2011 Elsevier B.V. All rights reserved.
Performance Characterization of Dye-Sensitized Photovoltaics under Indoor Lighting
(2017-04-20)
Chen, Chia-Yuan
;
Jian, Zih-Hong
;
Huang, Shih-Han
;
Lee, Kun-Mu
;
Kao, Ming-Hsuan
Indoor utilization of emerging photovoltaics is promising; however, efficiency characterization under room lighting is challenging. We report the first round-robin interlaboratory study of performance measurement for dye-sensitized photovoltaics (cells and mini-modules) and one silicon solar cell under a fluorescent dim light. Among 15 research groups, the relative deviation in power conversion efficiency (PCE) of the samples reaches an unprecedented 152%. On the basis of the comprehensive results, the gap between photometry and radiometry measurements and the response of devices to the dim illumination are identified as critical obstacles to the correct PCE. Therefore, we use an illuminometer as a prime standard with a spectroradiometer to quantify the intensity of indoor lighting and adopt the reverse-biased current voltage (I-V) characteristics as an indicator to qualify the I-V sampling time for dye-sensitized photovoltaics. The recommendations can brighten the prospects of emerging photovoltaics for indoor applications.
The influence of tetrapod-like ZnO morphology and electrolytes on energy conversion efficiency of dye-sensitized solar cells
(2010-12-01)
Lee, Chia-Hua
;
Chiu, Wei-Hao
;
Lee, Kun-Mu
;
Yen, Wen-Hsiang
;
Lin, Hsiu-Fen
Tetrapod-like ZnO nanostructures prepared by dc plasma technology were used as photoelectrodes in dye-sensitized solar cells (DSSCs) Each of the tetrapod-like ZnO possesses four extended arms that offer improved electron transport properties Tetrapod-like ZnO with short (S-ZnO) and long arms (L-ZnO) were synthesized by controlling the plasma gas flow and the input power Between these two tetrapod-like ZnO nanopowders the DSSCs using S-ZnO showed higher energy conversion efficiency than using L-ZnO This is due to the resulting increase in dye adsorption and enhanced short-circuit current density using S-ZnO Electrochemical Impedance spectroscopy (EIS) shows that the properties of electron transport of S-ZnO are superior to that of the L-ZnO We investigated the effect of the redox electrolytes (12) and the additives (Lil and TBP) on the performance of the DSSCs by intensity-modulated photovoltage spectroscopy and EIS (C) 2010 Elsevier Ltd All rights reserved