Browsing by Author "Hsu, Shun-Ju"

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Design and characterization of highly efficient porphyrin sensitizers for green see-through dye-sensitized solar cells
(2009)
Lu, Hsueh-Pei
;
Mai, Chi-Lun
;
Tsia, Chen-Yuan
;
Hsu, Shun-Ju
;
Hsieh, Chou-Pou
YD12 (eta = 6.7%) is a green sensitizer remarkable for its outstanding cell performance beyond that of N719 (eta = 6.1%) with no added scattering layer; the additional scattering layer assists N719 in promoting the efficiency in the red shoulder of the spectrum, but has only a small effect on the improvement of the cell performance for porphyrins.
Preparation and Photovoltaic Characterization of Free-Base and Metallo Carboxyphenylethynyl Porphyrins for Dye-Sensitized Solar Cells
(2010-10-01)
Lin, Ching-Yao
;
Lo, Chen-Fu
;
Hsieh, Min-Hsu
;
Hsu, Shun-Ju
;
Lu, Hsueh-Pei
Free-base, manganese, iron, cobalt, nickel, copper and zinc 5-(4-carboxy-phenylethyny1)-10,20-biphenylporphines are synthesized to study the impact of central metal ions to the photovoltaic performance of the solar cells.
Preparation and Spectral, Electrochemical, and Photovoltaic Properties of Acene-Modified Zinc Porphyrins
(2010-01-14)
Lin, Ching-Yao
;
Wang, Yu-Chien
;
Hsu, Shun-Ju
;
Lo, Chen-Fu
;
Diau, Eric Wei-Guang
A series of acene-modified zinc porphyrins (benzene to pentacene, denoted as LAC-1 to LAC-5) were prepared to study their absorption spectra, electrochemical properties, and photovoltaic properties. For the absorption spectral changes in THF, porphyrin B bands are red-shifted and broadened from 449 to 501 nm for LAC-I to LAC-3, showing the effect of additional pi-conjugation. In contrast, the B bands of LAC-4 and LAC-5 are blue-shifted. In addition, the tetracenyl group of LAC-4 gives rise to absorption bands in between B and Q bands. On the other hand, the Q bands of LAC-1 to LAC-5 are systematically broadened and red-shifted from 629 to 751 nm. By comparison, the absorption bands of LAC porphyrins on TiO(2) films are broadened and slightly shifted. Fluorescence emission maxima of LAC porphyrins in THF are also systematically red-shifted from LAC-1 to LAC-5. Cyclic voltammetry experiments in THF/TBAP show that the first reductions are systematically positive-shifted from -1.16 to -0.85 V vs SCE for LAC-1 to LAC-5, indicating the effect of increasing pi-conjugation. As for the performance of DSSCs using LAC porphyrins, the overall efficiency are LAC-1 (2.95%), LAC-2 (3.31%), LAC-3 (5.44%), LAC-4 (2.82%), and LAC-5 (0.10%). Overall efficiency of a LAC-3-sensitized solar cell is nearly twice of that of a LAC-1-sensitized solar cell and is about 81% overall efficiency of N719-sensitized solar cells under the same experimental conditions. The conversion efficiency of incident photons to current (IPCE) experiments shows that the broadened absorption bands of LAC-3 effectively minimizes the gap between B and Q bands, contributing to the improved DSSC performance. The very poor performance of LAC-5 is suggested to be caused by rapid nonradiative relaxation of the molecule in the singlet excited state.
Synthesis and characterization of porphyrin sensitizers with various electron-donating substituents for highly efficient dye-sensitized solar cells
(2010)
Hsieh, Chou-Pou
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Lu, Hsueh-Pei
;
Chiu, Chien-Lan
;
Lee, Cheng-Wei
;
Chuang, Shu-Han
A series of porphyrin dyes with an electron-donating group (EDG) attached at a meso-position (YD1-YD8) have been designed and synthesized for use as sensitizers in dye-sensitized solar cells (DSSC). The nature of the EDG exerts a significant influence on the spectral, electrochemical and photovoltaic properties of these sensitizers. Absorption spectra of porphyrins having an amino group show broadened Soret band and red-shifted Q bands with respect to those of reference porphyrin YD0. This phenomenon is more pronounced for porphyrins YD7 and YD8 that have a pi-conjugated triphenylamine at the meso-position opposite the anchoring group. Upon introduction of an EDG at the meso-position, the potential for the first oxidation alters significantly to the negative whereas that for the first reduction changes inappreciably, indicating a decreased HOMO-LUMO gap. Results of density-functional theory (DFT) calculations support the spectroelectrochemical data for a delocalization of charge between the porphyrin ring and the amino group in the first oxidative state of diarylamino-substituted porphyrins YD1-YD4, which exhibit superior photovoltaic performance among all porphyrins under investigation. With long-chain alkyl groups on the diarylamino substituent, YD2 shows the best cell performance with J(SC) = 13.4 mA cm(-2), V(OC) = 0.71 V, and FF = 0.69, giving an overall efficiency 6.6% of power conversion under simulated one-sun AM1.5 illumination.
Tuning Spectral and Electrochemical Properties of Porphyrin-Sensitized Solar Cells
(2010-07-15)
Lo, Chen-Fu
;
Hsu, Shun-Ju
;
Wang, Chin-Li
;
Cheng, Yi-Hui
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Lu, Hsueh-Pei
Phenylethynyl-substituted porphyrin (PEI) sensitizers bearing a nitro, cyano, methoxy, or dimethylamino phenylethynyl substituent were prepared to examine the electron-donating or -withdrawing effects of dyes on the photovoltaic performance of the corresponding dye-sensitized solar cells. The overall efficiencies of power conversion of the devices show a systematic trend Me(2)N-PE1 > MeO-PE1 > CN-PE1 > NO(2)-PE1, for which Me(2)N-PE1 has a device performance about 90% of that of a N719-sensitized solar cell under the same experimental conditions. The superior performance of Me(2)N-PE1 is attributed to the effective electron-donating property of the dye that exhibits broadened and red-shifted spectral features. According to frontier orbitals based on DFT calculations, the electrons are effectively injected from the dye to TiO(2) for Me(2)N-PE1 and MeO-PE1 upon excitation, but that driving force reverses for NO(2)-PE1. Electrochemical tests indicate that both LUMO and HOMO levels show a systematic trend Me(2)N-PE1 > MeO-PE1 > CN-PE1 > NO(2)-PE1, consistent with the trend of variation of the short-circuit currents in this series of sensitizers.