Effects of structure and electronic properties of D-π-A organic dyes on photovoltaic performance of dye-sensitized solar cells

Min Woo Lee, Jae Yup Kim, Hyung Geun Lee, Hyun Gil Cha, Duck Hyung Lee, Min Jae Ko

Research output: Contribution to journalArticle

Abstract

Herein, we examine the performance of dye-sensitized solar cells containing five D-π-A organic dyes designed by systematic modification of π-bridge size and geometric structure. Each dye has a simple push-pull structure with a triarylamino group as an electron donor, bithiophene-4,4-dimethyl-4H-cyclopenta[1,2-b:5,4-b’]dithiophene (M11), 4,4-dimethyl-4H-cyclopenta[1,2-b:5,4-b’]dithiophene-thiophene (M12), thiophene-4,4-dimethyl-4H-cyclopenta[1,2-b:5,4-b’]dithiophene (M13), 4,4-dimethyl-4H-cyclopenta[1,2-b:5,4-b’]dithiophene-benzene (M14), and 4,4-dimethyl-4H-cyclopenta[1,2-b:5,4-b’]dithiophene (M15) units as π-bridges, and cyanoacrylic acid as an electron acceptor/anchor. The extension of the π-bridge linkage favors wide-range absorption but, because of the concomitant molecular volume increase, hinders the efficient adsorption of dyes on the TiO2 film surface. Hence, higher loadings are achieved for smaller dye molecules, resulting in (i) a shift of the TiO2 conduction band edge to more negative values, (ii) a greater photocurrent, and (iii) suppressed charge recombination between the photoanode and the redox couple in the electrolyte. Consequently, under one-sun equivalent illumination (AM 1.5 G, 100 mW/cm2), the highest photovoltage, photocurrent, and conversion efficiency (η = 7.19%) are observed for M15, which has the smallest molecular volume among M series dyes.

Original languageEnglish
Pages (from-to)208-216
Number of pages9
JournalJournal of Energy Chemistry
Volume54
DOIs
StatePublished - 2021 Mar

Keywords

  • Donor-acceptor dyes
  • Dye-sensitized solar cells
  • Electron-rich unit
  • Impedance spectroscopy
  • Wide-range absorption

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