title: Conjugated phosphonic acid modified zinc oxide electron transport layers for improved performance in organic solar cells.
abstract: Phosphonic acid modification of zinc oxide (ZnO) electron transport layers in inverted P3HT:ICBA solar cells was studied to determine the effect of conjugated linkages between the aromatic and phosphonic acid attachment groups. For example, zinc oxide treated with 2,6-difluorophenylvinylphosphonic acid, having a conjugated vinyl group connecting the aromatic moiety to the phosphonic acid group, showed a 0.78 eV decrease in the effective work function versus unmodified ZnO, whereas nonconjugated 2,6-difluorophenylethylphosphonic acid resulted in a 0.57 eV decrease, as measured by Kelvin probe. This resulted in an average power conversion efficiency of 5.89% for conjugated 2,6-difluorophenyvinylphosphonic acid modified solar cells, an improvement over unmodified (5.24%) and nonconjugated phosphonic acid modified devices (5.64%), indicating the importance of the conjugated linkage.
authors.affiliation: Department of Physics and §Department of Chemistry and Geochemistry, Colorado School of Mines , Golden, Colorado 80401, United States.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Braid
authors.forename: Unsal
authors.initials: U
authors.lastname: Koldemir
authors.forename: Alan
authors.initials: A
authors.lastname: Sellinger
authors.forename: Reuben T
authors.initials: RT
authors.lastname: Collins
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Furtak
authors.forename: Dana C
authors.initials: DC
authors.lastname: Olson
keywords: conjugated linkage; inverted devices; organic photovoltaics; phosphonic acid; work function tuning