title: Efficient energy sensitization of C60 and application to organic photovoltaics.
abstract: Fullerenes are currently the most popular electron-acceptor material used in organic photovoltaics (OPVs) due to their superior properties, such as good electron conductivity and efficient charge separation at the donor/acceptor interface. However, low absorptivity in the visible spectral region is a significant drawback of fullerenes. In this study, we have designed a zinc chlorodipyrrin derivative (ZCl) that absorbs strongly in the visible region (450-600 nm) with an optical density 7-fold higher than a C60 film. ZCl efficiently transfers absorbed photoenergy to C60 in mixed films. Application of ZCl as an energy sensitizer in OPV devices leads to an increase in the photocurrent from the acceptor layer, without changing the other device characteristics, i.e., open circuit voltage and fill factor. For example, C60-based OPVs with and without the sensitizer give 4.03 and 3.05 mA/cm(2), respectively, while both have V(OC) = 0.88 V and FF = 0.44. Our ZCl sensitization approach improves the absorbance of the electron-acceptor layer while still utilizing the beneficial characteristics of C60 in OPVs.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Cong
authors.initials: C
authors.lastname: Trinh
authors.forename: Kent O
authors.initials: KO
authors.lastname: Kirlikovali
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Bartynski
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Tassone
authors.forename: Michael F
authors.initials: MF
authors.lastname: Toney
authors.forename: George F
authors.initials: GF
authors.lastname: Burkhard
authors.forename: Michael D
authors.initials: MD
authors.lastname: McGehee
authors.forename: Peter I
authors.initials: PI
authors.lastname: Djurovich
authors.forename: Mark E
authors.initials: ME
authors.lastname: Thompson