Dependence of the Device Performance of Polymer Solar Cells on the Insertion of Metal Nanoparticle Layers at the Electron-collecting Electrodes

Abstract

We report a study of the dependence of the device performance of polymer solar cells with the blend films of regioregular poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C₆₁-butyric acid methyl ester (PCBM) on the insertion of a layer of metal (Pd, Ag, Cu or Au) nanoparticles (NPs) at the electron-collecting electrodes. The short-circuit current density, the incident photo-to-current conversion efficiency, and the power conversion efficiency of the cells increased by the insertion of metal-NPs; the insertion of the Pd-NP layer has a large enhancement effect for the device performance. The light absorption was found to increase by forming the Pd-NP layer on the blend film without changing the light reflection. The formation of Au NPs on the blend films was directly observed by scanning tunneling microscopy (STM). The possible mechanism for such improvement is discussed using the results of the solar-cell parameters and the STM.