Effect of Metal-Reflection and Surface-Roughness Properties on Power-Conversion Efficiency for Polymer Photovoltaic Cells

We investigated the effect of the reflectivity of various metal cathodes on the power-conversion efficiency (PCE) of organic photovoltaic (OPV) cells fabricated with a P3HT:PCBM blended layer. The reflectivity of the cathodes correlated well with the short-circuit Current (J(sc)) influenced by absorption of visible light reflected from the cathodes; that is, a higher reflectivity of the cathodes led to a higher J(sc). In addition, we analyzed how the surface roughness of a metal cathode influences the performance on the polymer PV cells. As a result, a higher reflectivity and a lower surface roughness of the metal cathodes gave a higher PCE. In addition, it was confirmed that the interface property between the metal cathodes and organic hole/exciton blocking layer strongly influences the PCE of OPV cells.