Sensitization effect by porphyrin in polythiophene/perylene dye two-layer solar cells

An enhanced photocurrent was observed for a two-layer cell consisting of a regioregular polythiophene (PTh) blended with metal-free porphyrin (H2tpp) and a perylene tetracarboxylic derivative (PV), compared to a PTh (without H2tpp)/PV two-layer cell. This is because photoexcited H2tpp molecules efficiently transfer holes to PTh molecules and then produced electrons in H2tpp molecules rapidly transfer to PV molecules at the mixed solid/PV interface. In the two-layer photocell with the mixed solid, H2tpp behaves as a sensitizer, PTh and PV solids as carrier transport layers, and the mixed solid/PV interface as a charge separation site. Power conversion efficiency attained to η=2.9% for the PTh (with H2tpp)/PV two-layer cell under monochromatic light with 6 μW cm−2 intensity.