title: Solution-processable low-molecular weight extended arylacetylenes: versatile p-type semiconductors for field-effect transistors and bulk heterojunction solar cells.
abstract: We report the synthesis and characterization of a series of five extended arylacetylenes, 9,10-bis-{[m,p-bis(hexyloxy)phenyl]ethynyl}-anthracene (A-P6t, 1), 9,10-bis-[(p-{[m,p-bis(hexyloxy) phenyl]ethynyl}phenyl)ethynyl]-anthracene (PA-P6t, 2), 4,7-bis-{[m,p-bis(hexyloxy)phenyl]ethynyl}-2,1,3-benzothiadiazole (BTZ-P6t, 5), 4,7-bis(5-{[m,p-bis(hexyloxy)phenyl]ethynyl}thien-2-yl)-2,1,3-benzothiadiazole (TBTZ-P6t, 6), and 7,7'-({[m,p-bis(hexyloxy)phenyl]ethynyl}-2,1,3-benzothiadiazol-4,4'-ethynyl)-2,5-thiophene (BTZT-P6t, 7), and two arylvinylenes, 9,10-bis-{(E)-[m,p-bis(hexyloxy)phenyl]vinyl}-anthracene (A-P6d, 3), 9,10-bis-[(E)-(p-{(E)-[m,p-bis(hexyloxy)phenyl]vinyl}phenyl)vinyl]-anthracene (PA-P6d, 4). Trends in optical absorption spectra and electrochemical redox processes are first described. Next, the thin-film microstructures and morphologies of films deposited from solution under various conditions are investigated, and organic field-effect transistors (OFETs) and bulk heterojunction photovoltaic (OPV) cells fabricated. We find that substituting acetylenic for olefinic linkers on the molecular cores significantly enhances device performance. OFET measurements reveal that all seven of the semiconductors are FET-active and, depending on the backbone architecture, the arylacetylenes exhibit good p-type mobilities (mu up to approximately 0.1 cm(2) V(-1) s(-1)) when optimum film microstructural order is achieved. OPV cells using [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) as the electron acceptor exhibit power conversion efficiencies (PCEs) up to 1.3% under a simulated AM 1.5 solar irradiation of 100 mW/cm(2). These results demonstrate that arylacetylenes are promising hole-transport materials for p-channel OFETs and promising donors for organic solar cells applications. A direct correlation between OFET arylacetylene hole mobility and OPV performance is identified and analyzed.
authors.affiliation: Department of Chemistry, the Argonne-Northwestern Solar Energy Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
authors.forename: Fabio
authors.initials: F
authors.lastname: Silvestri
authors.forename: Assunta
authors.initials: A
authors.lastname: Marrocchi
authors.forename: Mirko
authors.initials: M
authors.lastname: Seri
authors.forename: Choongik
authors.initials: C
authors.lastname: Kim
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks
authors.forename: Antonio
authors.initials: A
authors.lastname: Facchetti
authors.forename: Aldo
authors.initials: A
authors.lastname: Taticchi