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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.
Turkovic et al. (Fri,) studied this question.