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New Branched Alkyl Tetrathienothiophene (TTAR)-Based Organic Sensitizers with Power Conversion Efficiency up to 11%

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-dimentional (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 %. Thus, TTAR-b8 is the highest performing fused-thiophene-based organic DSSC dye reported to date.

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Publication details

The article was received on 28 Feb 2017, accepted on 26 Apr 2017 and first published on 27 Apr 2017


Article type: Paper
DOI: 10.1039/C7TA01825H
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    New Branched Alkyl Tetrathienothiophene (TTAR)-Based Organic Sensitizers with Power Conversion Efficiency up to 11%

    Y. Ezhumalai, B. Lee, M. Fan, B. Harutyunyan, K. Prabakaran, C. Lee, S. H. Chang, J. Ni, S. Vegiraju, P. Priyanka, Y. Wu, C. Liu, S. Yau, J. T. Lin, C. Wu, M. J. Bedzyk, M. M. Chen, K. Ho, R. Chang and T. Marks, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA01825H

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