Stability and photodegradation mechanisms of conjugated polymer/fullerene plastic solar cells

Degradation studies of poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene-vinylene) (MDMO-PPV), fullerenes ((6,6)-phenyl C61- butyric acid methyl ester (PCBM) and C60), and mixtures, which are the photoactive components in plastic solar cells, are shown. The degradation processes of the individual components and of a 1 : 3 mixture are characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and by current/voltage (I–V) measurements of devices under the influence of light and oxygen. A faster degradation rate was found for the polymer compared with C60. In composites with fullerenes, the stability of MDMO-PPV is enhanced due to the fast electron transfer to C60.