Browsing by Author "Pan, Tsung-Yu"

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A fluorene-modified porphyrin for efficient dye-sensitized solar cells
(2012)
Wu, Cheng-Hua
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Pan, Tsung-Yu
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Hong, Shang-Hao
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Wang, Chin-Li
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Kuo, Hshin-Hui
Porphyrins bearing a polyaromatic or a heterocyclic group are prepared to study their fundamental and photovoltaic properties. Solar cells sensitized with a fluorene-modified porphyrin outperform other dyes in the series, reaching similar to 90% efficiency of N719 dye.
A strategy to design highly efficient porphyrin sensitizers for dye-sensitized solar cells
(2011)
Chang, Yu-Cheng
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Wang, Chin-Li
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Pan, Tsung-Yu
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Hong, Shang-Hao
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Lan, Chi-Ming
We designed highly efficient porphyrin sensitizers with two phenyl groups at meso-positions of the macrocycle bearing two ortho-substituted long alkoxyl chains for dye-sensitized solar cells; the ortho-substituted devices exhibit significantly enhanced photovoltaic performances with the best porphyrin, LD14, showing J(SC) = 19.167 mA cm(-2), V(OC) = 0.736 V, FF = 0.711, and overall power conversion efficiency eta = 10.17%.
Design and characterization of alkoxy-wrapped push-pull porphyrins for dye-sensitized solar cells
(2012)
Ripolles-Sanchis, Teresa
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Guo, Bo-Cheng
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Wu, Hui-Ping
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Pan, Tsung-Yu
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Lee, Hsuan-Wei
Three alkoxy-wrapped push-pull porphyrins were designed and synthesized for dye-sensitized solar cell (DSSC) applications. Spectral, electrochemical, photovoltaic and electrochemical impedance spectroscopy properties of these porphyrin sensitizers were well investigated to provide evidence for the molecular design.
Enhanced photovoltaic performance with co-sensitization of porphyrin and an organic dye in dye-sensitized solar cells
(2012-04-01)
Lan, Chi-Ming
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Wu, Hui-Ping
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Pan, Tsung-Yu
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Chang, Chia-Wei
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Chao, Wei-Shan
We designed a stepwise approach for co-sensitization of a zinc porphyrin sensitizer (LD12) with a spirally configured organic dye (CD5) for dye-sensitized solar cells. The co-sensitized LD12 + CD5 device showed significantly enhanced V-OC and J(SC) relative to its individual single-dye sensitized devices. Upon optimization, the device made of the LD12 + CD5 system yielded J(SC)/mA cm(-2) = 16.7, V-OC/V = 0.74, FF = 0.73 and eta = 9.0%; this performance is superior to that of either individual device made from LD12 (eta = 7.5%) and CD5 (eta = 5.7%) under the same conditions of fabrication. To understand the effects of the potential shift and charge recombination on the cell performance, we measured charge-extraction (CE) and intensity-modulated photovoltage spectra (IMVS). Upon sensitization with each dye, the TiO2 potentials are similar, but co-sensitization causes the potential to shift down (cathodic shift). Charge recombination was significantly retarded for the co-sensitized system relative to each individual dye-sensitized system, to account for the enhanced V-OC for the former relative to the latter. A test of stability indicates a systematic trend between the LD12 + CD5 and LD12 devices; the performance of the co-sensitized device degraded only similar to 15% and remained stable during the period of 500-1000 h near 295 K.
Enveloping porphyrins for efficient dye-sensitized solar cells
(2012-05-01)
Wang, Chin-Li
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Lan, Chi-Ming
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Hong, Shang-Hao
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Wang, Yi-Fen
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Pan, Tsung-Yu
A series of porphyrins bearing alkoxyl and/or alkyl chains were prepared to investigate the roles of alkoxyl/alkyl chains in the enhanced photovoltaic performance of the dyes. Based on the experimental results and the molecular simulations, we demonstrated that suitable long alkoxyl chains are capable of wrapping the porphyrin core, thus resulting in decreased dye aggregation, elevated excited states and LUMOs, and improved photovoltaic performance.
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.
Porphyrin sensitizers with pi-extended pull units for dye-sensitized solar cells
(2013)
Reddy, Nagannagari Masi
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Pan, Tsung-Yu
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Rajan, Yesudoss Christu
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Guo, Bo-Cheng
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Lan, Chi-Ming
New pi-extended porphyrin dyes YD26-YD29 with long alkoxyl chains at the ortho positions of the meso-phenyls, and meta di-tert-butylphenyl-substituted porphyrins YD12-CN, and YD13-CN were synthesized for dye-sensitized solar cells, and their optical, electrochemical and photovoltaic properties were investigated and compared with those of YD12 and YD13. The absorption spectra of YD26-YD29 showed a slight red shift of Soret bands and blue shift of Q bands as compared to the meta-substituted porphyrins due to the electron-donating effects of dioctyloxy substituents at the ortho-positions of the meso-phenyl rings. Replacement of the carboxyl with a cyanoacrylic acid as the anchoring group results in significant broadening and red shifts of the absorptions, which is due to the strong electronic coupling between the pull unit and the porphyrin ring facilitated by the C C triple bond. The electrochemical studies and quantum-chemical calculations (DFT) indicated that the ortho alkoxy-substituted sensitizers exhibit lower oxidation potential, i.e. a higher HOMO energy level, and their HOMO-LUMO gaps are comparable to the meta-substituted analogues. The photovoltaic measurements confirmed that the ortho-octyloxy groups in the two meso-phenyls of YD26 and YD27 play a significant role in preventing dye aggregation thereby enhancing the corresponding short-circuit current density and open-circuit voltage. The power conversion efficiency (eta) of YD26 is 8.04%, which is 11% higher than that of YD12, whereas the efficiency of YD27 is 6.03%, which is 135% higher than that of YD13. On the other hand, the poor performance of YD28 and YD29 is due to the floppy structural nature and limited molecular rigidity of the cyanoacrylic acid anchor.