Browsing by Author "Chuang, Shu-Han"

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Design and characterization of porphyrin sensitizers with a push-pull framework for highly efficient dye-sensitized solar cells
(2010)
Wu, Sung-Lin
;
Lu, Hsueh-Pei
;
Yu, Han-Ting
;
Chuang, Shu-Han
;
Chiu, Chien-Lan
Novel porphyrin dyes YD14-YD17 with a push-pull framework were synthesized for dye-sensitized solar cells (DSSC); their spectral, electrochemical and photovoltaic properties were investigated. The absorption bands of these porphyrin dyes are broadened and red-shifted upon introduction of electron-donating groups (EDG) to the meso-positions via extension of p-conjugation. Electrochemical tests show that the first oxidation for these porphyrins occurs at a potential greater than that of the I(-)/I(3)(-) redox couple, and attachment of EDGs to the periphery of the porphyrin facilitates electron abstraction. The photovoltaic measurements show that YD14 and YD17 have a power conversion efficiency of similar to 7%. Introduction of EDGs to various meso-positions is demonstrated to be achievable, and porphyrin dyes with appropriate EDGs are promising candidates for highly efficient DSSCs.
Porphyrin-Perylene Dyes for Dye-Sensitized Solar Cells
(2010-10-01)
Chen, Hong-Yi
;
Lu, Hsueh-Pei
;
Lee, Cheng-Wei
;
Chuang, Shu-Han
;
Diau, Eric Wei-Guang
Two novel porphyrin-perylene dyads 1 and 2 for DSSC applications have been synthesized. The absorption band of the perylene fills up the trough between the Soret and Q bands of the porphyrin, leading to an increase in the absorption efficiency of the dye. The highly conjugated acetylenic bridge mediates strong electronic coupling between the porphyrin and perylene units and results in the extension of it-conjugation of the porphyrin ring. The Soret and Q bands are broadened and red-shifted and the light-harvesting effect is thus improved. We propose that energy transfer occurs from the photoexcited perylene to porphyrin for dyad 1 whereas energy transfer proceeds from the excited porphyrin to perylene for dyad 2. Our studies show that multichromophoric dyes used for DSSC can be designed in a rational manner with predictable photophysical behavior and efficient light-harvesting properties, but the efficiency of the energy transfer process in a consecutive model needs to be controlled for a significant improvement of the cell performance using perylene-porphyrin sensitizers.
Synthesis and characterization of porphyrin sensitizers with various electron-donating substituents for highly efficient dye-sensitized solar cells
(2010)
Hsieh, Chou-Pou
;
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.