title: Long-term stabilization of organic solar cells using hindered phenols as additives.
abstract: We report on the improvement of long-term stability of organic solar cells (OPV) using hindered phenol based antioxidants as stabilizing additives. A set of seven commercially available hindered phenols are investigated for use in bulk-heterojunction OPV. Polymer:fullerene films based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are characterized with respect to the initial power conversion efficiency and the long-term stability improvement under illumination in ambient conditions. FTIR spectroscopy is used to trace chemical degradation over time. OPV performance is recorded under ISOS-3 conditions, and an improved long-term performance of OPV devices, manifested in increased accumulated power generation (APG), is found for octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Using this additive, APG is increased by a factor of 3 compared to the reference. Observed differences in the stabilization of tested additives are discussed in terms of energetic trap states formation within the HOMO/LUMO gap of the photoactive material, morphological changes, and chemical structure.
authors.affiliation: Institute of Physics and Institute of Micro- and Nanotechnologies, Ilmenau University of Technology , 98683 Ilmenau, Germany.
authors.forename: Vida
authors.initials: V
authors.lastname: Turkovic
authors.forename: Sebastian
authors.initials: S
authors.lastname: Engmann
authors.forename: Nikos
authors.initials: N
authors.lastname: Tsierkezos
authors.forename: Harald
authors.initials: H
authors.lastname: Hoppe
authors.forename: Uwe
authors.initials: U
authors.lastname: Ritter
authors.forename: Gerhard
authors.initials: G
authors.lastname: Gobsch
keywords: antioxidant; hydrogen donor; lifetime; radical scavenger; stabilizer; ternary blend