Porphyrin-oligothiophene conjugates as additives for P3HT/PCBM solar cells

The power conversion efficiency (PCE) of poly(3-hexylthiophene)/fullerene (P3HT/PCBM) bulk heterojunction solar cells is enhanced through the addition of Ni(II) porphyrin-oligothiophene conjugates to typical P3HT/PCBM blends. The introduction of the porphyrin dyes increases the efficiency by up to 63 +/- 20% compared with P3HT/PCBM control devices containing no additives. Moreover, external quantum efficiency (EQE) measurements show a 10 +/- 5% enhancement in photocurrent compared to control blends. These results lead us to conclude that the photo-induced dissociation of P3HT excitons is promoted in the presence of the Ni(II) porphyrin-oligothiophenes and that the Ni(II) porphyrin subunits act as light-harvesting sensitizers as well as energy conduits for the P3HT excitons at P3HT/PCBM interfaces