Metal-Free Tetrathienoacene Sensitizers for High-Performance Dye-Sensitized Solar Cells

Nanjia Zhou, Kumaresan Prabakaran, Byunghong Lee, Sheng Hsiung Chang, Boris Harutyunyan, Peijun Guo, Melanie R. Butler, Amod Timalsina, Michael J. Bedzyk, Mark A Ratner, Sureshraju Vegiraju, Shuehlin Yau, Chun Guey Wu, Robert P. H. Chang, Antonio Facchetti, Ming Chou Chen, Tobin J Marks

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160 Citations (Scopus)

Abstract

A new series of metal-free organic chromophores (TPA-TTAR-A (1), TPA-T-TTAR-A (2), TPA-TTAR-T-A (3), and TPA-T-TTAR-T-A (4)) are synthesized for application in dye-sensitized solar cells (DSSC) based on a donor-π-bridge-acceptor (D-π-A) design. Here a simple triphenylamine (TPA) moiety serves as the electron donor, a cyanoacrylic acid as the electron acceptor and anchoring group, and a novel tetrathienoacene (TTA) as the π-bridge unit. Because of the extensively conjugated TTA π-bridge, these dyes exhibit high extinction coefficients (4.5-5.2 × 104 M-1 cm-1). By strategically inserting a thiophene spacer on the donor or acceptor side of the molecules, the electronic structures of these TTA-based dyes can be readily tuned. Furthermore, addition of a thiophene spacer has a significant influence on the dye orientation and self-assembly modality on TiO2 surfaces. The insertion of a thiophene between the π-bridge and the cyanoacrylic acid anchoring group in TPA-TTAR-T-A (dye 3) promotes more vertical dye orientation and denser packing on TiO2 (molecular footprint = 79 Å2), thus enabling optimal dye loading. Using dye 3, a DSSC power conversion efficiency (PCE) of 10.1% with Voc = 0.833 V, Jsc = 16.5 mA/cm2, and FF = 70.0% is achieved, among the highest reported to date for metal-free organic DSSC sensitizers using an I-/I3- redox shuttle. Photophysical measurements on dye-grafted TiO2 films reveal that the additional thiophene unit in dye 3 enhances the electron injection efficiency, in agreement with the high quantum efficiency. (Graph Presented)

Original languageEnglish
Pages (from-to)4414-4423
Number of pages10
JournalJournal of the American Chemical Society
Volume137
Issue number13
DOIs
Publication statusPublished - Apr 8 2015

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ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

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