Metal-free branched alkyl tetrathienoacene (TTAR)-based sensitizers for high-performance dye-sensitized solar cells

Yamuna Ezhumalai, Byunghong Lee, Miao Syuan Fan, Boris Harutyunyan, Kumaresan Prabakaran, Chuan Pei Lee, Sheng Hsiung Chang, Jen Shyang Ni, Sureshraju Vegiraju, Pragya Priyanka, Ya Wen Wu, Chia Wei Liu, Shuehlin Yau, Jiann T. Lin, Chun Guey Wu, Michael J. Bedzyk*, Robert P.H. Chang, Ming Chou Chen, Kuo Chuan Ho, Tobin J. Marks

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

A new series of metal-free alkylated tetrathienoacene (TTAR)-based organic chromophores, TPA-TTAR-TA (R = branched-C8H17, 1, TTAR-b8; R = C15H31, 2, TTAR-15; R = C9H19, 3, TTAR-9), are synthesized for application in dye-sensitized solar cells (DSSCs). Due to the extensively conjugated TTAR π-bridge, all three dyes exhibit high extinction coefficients (1 × 105 M-1 cm-1). By systematically exploring the effects of the TTAR alkyl chain substituents, a significant influence of the dye coverage (orientation) on the TiO2 surfaces is observed. The branched-alkyl TTAR-b8 (1) promotes significant tilting and packing distortion on TiO2 in comparison to more ordered monolayers of linear long alkyls TTAR-15 (2) and TTAR-9 (3). Photophysical measurements on the dye-grafted TiO2 films reveal that the branched-alkylated TTA unit in 1 enhances the electron injection efficiency, in agreement with the high quantum efficiency. Notably, by utilizing a three-dimensional (3D) photonic crystal (PhC) layer to enhance the coherent scattering an increase the light absorption, TTAR-b8 exhibits higher short-circuit current densities and achieved a high PCE of 11.18%. TTAR-b8 is thus the best performing fused-thiophene-based organic DSSC dye reported to date.

Original languageEnglish (US)
Pages (from-to)12310-12321
Number of pages12
JournalJournal of Materials Chemistry A
Volume5
Issue number24
DOIs
StatePublished - 2017

ASJC Scopus subject areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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