Stability of bilayer trimethine cyanine dye/fullerene organic solar cells

The long-term (up to 100 days) stabilities of thin films of a trimethine cyanine dye (Cy3-P) and of Cy3-P/C60 bilayer solar cells with initial power conversion efficiencies of up to 3.6% in the regular and inverted device architecture were studied. For storage conditions under nitrogen at room temperature in the dark, Cy3-P films were stable and no decrease in performance was measured for inverted ITO/TiO2/C60/Cy3-P/MoO3/Ag solar cells. ITO/PEDOT:PSS and aluminum were found to be responsible for a slight inherent degradation of regular solar cells under inert storage conditions. Solar cells stressed at accelerated (80 °C) full sun simulation showed a burn-in period of ~5 days with a performance loss of 75%. This initial performance decrease might be linked to the photopolymerization reaction of C60. For longer times, performances stabilized and arrived at 15% of the initial values after a test period of 17 days.