title: Arylamine-based squaraine donors for use in organic solar cells.
abstract: Squaraine (SQ) dyes are notable for their exceptionally high absorption coefficients extending from the green to the near-infrared. In this work, we utilize the functionalized SQ donor: 2,4-bis [4-(N-phenyl-1-naphthylamino)-2,6-dihydroxyphenyl] squaraine (1-NPSQ) by substitution of isobutylamines in the common "parent SQ" with arylamines to improve stacking and hence exciton and charge transport. The strong electron-withdrawing arylamine group results in a highest occupied molecular orbital energy of 5.3 eV, compared to 5.1 eV for the parent SQ, making 1-NPSQ a suitable donor when used with a C(60) acceptor in an organic photovoltaic cell. Optimized and thermally annealed, nanocrystalline heterojunction 1-NPSQ/C(60)/bathocuproine solar cells with an open circuit voltage of 0.90 ± 0.01 V, fill factor of 0.64 ± 0.01, and short circuit current of 10.0 ± 1.1 mA/cm(2) at 1 sun, AM1.5G illumination (solar spectrally corrected) result in a power conversion efficiency of 5.7 ± 0.6%. Crystallograpnic data suggest that the intermolecular stacking of 1-NPSQ molecules is closer than that of the parent SQ, thereby reducing the device series resistance and increasing its fill factor.
authors.affiliation: Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, Ann Arbor, Michigan 48109, United States.
authors.forename: Guodan
authors.initials: G
authors.lastname: Wei
authors.forename: Xin
authors.initials: X
authors.lastname: Xiao
authors.forename: Siyi
authors.initials: S
authors.lastname: Wang
authors.forename: Jeramy D
authors.initials: JD
authors.lastname: Zimmerman
authors.forename: Kai
authors.initials: K
authors.lastname: Sun
authors.forename: Vyacheslav V
authors.initials: VV
authors.lastname: Diev
authors.forename: Mark E
authors.initials: ME
authors.lastname: Thompson
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Forrest