Effect of annealing on the characteristics of organic solar cells: Polymer blends with a 2-vinyl-4,5-dicyanoimidazole derivative

Photovoltaic cells based on blends of either regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) or a poly(phenylenevinylene) (A-PPE-PPV) derivative as electron donors with a novel electron acceptor based on 2-vinyl-4,5-dicyanoimidazole (Vinazene) have been investigated in detail. We found a strong influence of annealing conditions on the thin-film nanostructure and device performance. By adjusting the material combinations, external quantum efficiencies between 12 and 15% and energy conversion efficiencies of 0.5% could be reached. Though comparable efficiencies with both donor polymers could be obtained with the Vinazene derivative as acceptor, we found strong indications that different mechanisms are limiting the device efficiency.