title: Structure-property relationship study of substitution effects on isoindigo-based model compounds as electron donors in organic solar cells.
abstract: We designed and synthesized a series of isoindigo-based derivatives to investigate how chemical structure modification at both the 6,6'- and 5,5'-positions of the core with electron-rich and electron-poor moieties affect photophysical and redox properties as well as their solid-state organization. Our studies reveal that 6,6'-substitution on the isoindigo core results in a stronger intramolecular charge transfer band due to strong electronic coupling between the 6,6'-substituent and the core, whereas 5,5'-substitution induces a weaker CT band that is more sensitive to the electronic nature of the substituents. In the solid state, 6,6'-derivatives generally form J-aggregates, whereas 5,5'-derivatives form H-aggregates. With only two branched ethylhexyl side chains, the 6,6'-derivatives form organized lamellar structures in the solid state. The incorporation of electron-rich benzothiophene, BT, substituents further enhances ordering, likely because of strong intermolecular donor-acceptor interactions between the BT substituent and the electron-poor isoindigo core on neighboring compounds. Collectively, the enhanced photophysical properties and solid-state organization of the 6,6'-benzothiophene substituted isoindigo derivative compared to the other isoindigo derivatives examined in this study resulted in solar cells with higher power conversion efficiencies when blended with a fullerene derivative.
authors.affiliation: Department of Chemical and Biological Engineering and ‡Princeton Center for Complex Materials, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Ren
authors.forename: Anna M
authors.initials: AM
authors.lastname: Hiszpanski
authors.forename: Luisa
authors.initials: L
authors.lastname: Whittaker-Brooks
authors.forename: Yueh-Lin
authors.initials: YL
authors.lastname: Loo
mesh_terms: D004583:Electrons; D007211:Indoles / Q000737:chemistry; D010777:Photochemistry
chemical_list: D007211:Indoles; C049010:isoindigotin
references.citation: J Am Chem Soc. 2013 Feb 13;135(6):2207-12
references.pmid: 23363295
references.citation: Acc Chem Res. 2013 Nov 19;46(11):2645-55
references.pmid: 23902284
references.citation: Adv Mater. 2014 Mar 26;26(12):1801-26
references.pmid: 24523218
references.citation: Adv Mater. 2014 Jan 22;26(3):471-6
references.pmid: 24178830
references.citation: J Am Chem Soc. 2012 Oct 10;134(40):16597-606
references.pmid: 22950622
references.citation: Angew Chem Int Ed Engl. 2012 Feb 27;51(9):2020-67
references.pmid: 22344682
references.citation: Acc Chem Res. 2012 May 15;45(5):723-33
references.pmid: 22288572
references.citation: Org Lett. 2010 Feb 19;12(4):660-3
references.pmid: 20099892
references.citation: ACS Nano. 2013 Jan 22;7(1):294-300
references.pmid: 23228001
references.citation: Chem Commun (Camb). 2012 Mar 25;48(25):3039-51
references.pmid: 22343975
references.citation: Acc Chem Res. 2014 Jan 21;47(1):257-70
references.pmid: 23984626
references.citation: Chemphyschem. 2012 Jun 4;13(8):2001-11
references.pmid: 22473631
references.citation: Phys Chem Chem Phys. 2013 Sep 28;15(36):15193-203
references.pmid: 23928904
references.citation: ACS Appl Mater Interfaces. 2011 Apr;3(4):1210-5
references.pmid: 21405105
references.citation: Org Biomol Chem. 2011 Sep 7;9(17):6127-32
references.pmid: 21755080
references.citation: Chem Soc Rev. 2012 Jun 7;41(11):4245-72
references.pmid: 22453295
references.citation: Phys Chem Chem Phys. 2013 Jun 21;15(23):8972-82
references.pmid: 23652780
references.citation: Nat Chem. 2012 Sep;4(9):699-704
references.pmid: 22914189