Significant improvement of optoelectronic and photovoltaic properties by incorporating thiophene in a solution-processable D–A–D modular chromophore

Raynor, Aaron M., Gupta, Akhil, Plummer, Christopher M., Jackson, Sam L., Bilic, Ante, Patil, Hemlata, Sonar, Prashant, & Bhosale, Sheshanath V. (2015) Significant improvement of optoelectronic and photovoltaic properties by incorporating thiophene in a solution-processable D–A–D modular chromophore. Molecules, 20(12), pp. 21787-21801.

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Abstract

Through the incorporation of a thiophene functionality, a novel solution-processable small organic chromophore was designed, synthesized and characterized for application in bulk-heterojunction solar cells. The new chromophore, (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)acrylonitrile) (coded as AS2), was based on a donor–acceptor–donor (D–A–D) module where a simple triphenylamine unit served as an electron donor, 1,4-phenylenediacetonitrile as an electron acceptor, and a thiophene ring as the π-bridge embedded between the donor and acceptor functionalities. AS2 was isolated as brick-red, needle-shaped crystals, and was fully characterized by 1H- and 13C-NMR, IR, mass spectrometry and single crystal X-ray diffraction. The optoelectronic and photovoltaic properties of AS2 were compared with those of a structural analogue, (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(4-(diphenylamino)phenyl)-acrylonitrile) (AS1). Benefiting from the covalent thiophene bridges, compared to AS1 thin solid film, the AS2 film showed: (1) an enhancement of light-harvesting ability by 20%; (2) an increase in wavelength of the longest wavelength absorption maximum (497 nm vs. 470 nm) and (3) a narrower optical band-gap (1.93 eV vs. 2.17 eV). Studies on the photovoltaic properties revealed that the best AS2-[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM)-based device showed an impressive enhanced power conversion efficiency of 4.10%, an approx. 3-fold increase with respect to the efficiency of the best AS1-based device (1.23%). These results clearly indicated that embodiment of thiophene functionality extended the molecular conjugation, thus enhancing the light-harvesting ability and short-circuit current density, while further improving the bulk-heterojunction device performance. To our knowledge, AS2 is the first example in the literature where a thiophene unit has been used in conjunction with a 1,4-phenylenediacetonitrile accepting functionality to extend the π-conjugation in a given D–A–D motif for bulk-heterojunction solar cell applications.

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ID Code: 99797
Item Type: Journal Article
Refereed: Yes
Keywords: solution-processable; bulk-heterojunction devices; donor–acceptor–donor; triphenylamine; thiophene; 1,4-phenylenediacetonitrile
DOI: 10.3390/molecules201219798
ISSN: 1420-3049
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2015 by the authors; licensee MDPI, Basel, Switzerland
Copyright Statement: This article is an open access article distributed under the terms and conditions of the Creative Commons by Attribution
(CC-BY) license (http://creativecommons.org/licenses/by/4.0/).
Deposited On: 11 Oct 2016 22:23
Last Modified: 14 Oct 2016 04:50

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