title: Significant Improvement of Optoelectronic and Photovoltaic Properties by Incorporating Thiophene in a Solution-Processable D-A-D Modular Chromophore.
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 (13)C-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.
authors.affiliation: School of Applied Sciences, The Royal Melbourne Institute of Technology (RMIT) University, GPO Box 2476, Melbourne Victoria 3001, Australia. aaron.raynor@rmit.edu.au.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Raynor
authors.affiliation: School of Applied Sciences, The Royal Melbourne Institute of Technology (RMIT) University, GPO Box 2476, Melbourne Victoria 3001, Australia. akhil.gupta@monash.edu.|Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville Victoria 3052, Australia. akhil.gupta@monash.edu.
authors.forename: Akhil
authors.initials: A
authors.lastname: Gupta
authors.affiliation: School of Applied Sciences, The Royal Melbourne Institute of Technology (RMIT) University, GPO Box 2476, Melbourne Victoria 3001, Australia. chris.plummer@rmit.edu.au.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Plummer
authors.affiliation: School of Applied Sciences, The Royal Melbourne Institute of Technology (RMIT) University, GPO Box 2476, Melbourne Victoria 3001, Australia. sam.jackson@rmit.edu.au.
authors.forename: Sam L
authors.initials: SL
authors.lastname: Jackson
authors.affiliation: Virtual Nanoscience Lab, Commonwealth Scientific and Industrial Research Organization (CSIRO) Manufacturing, Parkville Victoria 3052, Australia. ante.bilic@csiro.au.
authors.forename: Ante
authors.initials: A
authors.lastname: Bilic
authors.affiliation: School of Applied Sciences, The Royal Melbourne Institute of Technology (RMIT) University, GPO Box 2476, Melbourne Victoria 3001, Australia. hemlatap2@gmail.com.
authors.forename: Hemlata
authors.initials: H
authors.lastname: Patil
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), GPO Box 2434, Brisbane QLD 4001, Australia. sonar.prashant@qut.edu.au.
authors.forename: Prashant
authors.initials: P
authors.lastname: Sonar
authors.affiliation: School of Applied Sciences, The Royal Melbourne Institute of Technology (RMIT) University, GPO Box 2476, Melbourne Victoria 3001, Australia. sheshanath.bhosale@rmit.edu.au.
authors.forename: Sheshanath V
authors.initials: SV
authors.lastname: Bhosale
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D055668:Photochemical Processes; D012993:Solar Energy; D012996:Solutions; D013876:Thiophenes / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; D012996:Solutions; D013876:Thiophenes
keywords: 1,4-phenylenediacetonitrile; bulk-heterojunction devices; donor–acceptor–donor; solution-processable; thiophene; triphenylamine