Plasmonic forward light scattering effect of size-controlled silver nanoparticles in organic photovoltaics

Abstract

In this report, plasmonic effects in organic photovoltaic cells are systematically analyzed using the size-controlled silver nanoparticles (AgNPs, diameter : 10~100nm), which were incorporated into the anodic buffer layer, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). We found that the optical property of AgNPs tuned by the size had considerable influence on the device performances. We verified the size-dependent scattering properties of the AgNPs with visualized AgNPs by NSOM (Near-field optical microscope) and analytic optical simulation. In addition, we found that the external quantum efficiency (EQE) was significantly enhanced near the LSPP with the absorption enhancement due to the plasmonic scattering effect. Significant EQE reduction when the sizes were bigger that 70nm caused by back scattering effects. The power conversion efficiency (PCE) approaching 7.6% was achieved from 6.4% of control devices in poly(N-9 -hept-decanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole) (PCDTBT) : [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) based-OPVs with AgNPs (diameter : 67nm) embedded. Finally, we analyzed the origin of plasmonic scattering effects by comparing experimental results and optical simulations and suggested how to utilize the LSPP of MNPs as an optical engineering tool in OPVs.