Impurity tolerance of polymer solar cells: The crucial role of palladium catalyst and its ligands

Polymer photovoltaic solar cells based on PTQ10:IT4F were fabricated and characterized with voluntary contamination of several impurities in various amounts. Impurities were selected as related to the Stille coupling reagents: in particular palladium catalysts and their respective ligands. Below a concentration of 300 ppm, the pristine device efficiencies were not significantly affected for any of the studied compounds. The degradation patterns under accelerated light soaking were not modified either. For higher impurities amounts (>300 ppm), Pd(PPh3)4 catalyst shows a strong poisoning effect on both pristine device performances and operating stability. Interestingly, we demonstrate that not only the metallic center of the catalytic complex, but also the ligands can play a role on the organic solar cells performances.