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Issue 31, 2015
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The cis-isomer performs better than the trans-isomer in porphyrin-sensitized solar cells: interfacial electron transport and charge recombination investigations

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Abstract

We report characterizations and device performance for dye-sensitized solar cells using cis- and trans-isomers of 2D–π–2A zinc porphyrins with carboxyphenyl and thienyl groups in their meso-positions. Under identical experimental conditions with similar dye loadings, we observed overall power conversion efficiencies of 2.44% and 0.88% for devices made of cis-2S2A and trans-2S2A, respectively. This uneven performance among cis and trans isomers under the same experimental conditions can be rationalized with detailed investigations via spectroscopic, quantum chemical, and femtosecond fluorescence up-conversion investigations. Density functional theory (DFT) calculations show that a small amount of electron density is localized over carboxyphenyl groups in the LUMO of cis-2S2A, but there is no electron density populated on the carboxyphenyl groups in the LUMO of trans-2S2A. The femtosecond fluorescence decay measurements revealed that the excited-state lifetime of trans-2S2A on Al2O3 is half of that of cis-2S2A on Al2O3. Moreover, the dye-to-TiO2 electron injection time of trans-2S2A is 2.54 ps, which is shorter than that of cis-2S2A/TiO2 (2.95 ps). Electrochemical impedance spectra measured under one sun illumination also revealed that the charge recombination time of cis-2S2A is longer than that of trans-2S2A. This thorough understanding of isomeric effects on the performance of porphyrins will serve as a guideline for the design of future sensitizing dyes for solar cells.

Graphical abstract: The cis-isomer performs better than the trans-isomer in porphyrin-sensitized solar cells: interfacial electron transport and charge recombination investigations

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Publication details

The article was received on 23 Apr 2015, accepted on 29 Jun 2015 and first published on 30 Jun 2015


Article type: Paper
DOI: 10.1039/C5CP02367J
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Phys. Chem. Chem. Phys., 2015,17, 20134-20143

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    The cis-isomer performs better than the trans-isomer in porphyrin-sensitized solar cells: interfacial electron transport and charge recombination investigations

    L. Luo, R. B. Ambre, S. B. Mane, E. W. Diau and C. Hung, Phys. Chem. Chem. Phys., 2015, 17, 20134
    DOI: 10.1039/C5CP02367J

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