Charge-carrier dynamics in hybrid plasmonic organic solar cells with Ag nanoparticles

To understand the effects of Ag nanoparticles NPs on the performance of organic solar cells, we examined the properties of hybrid poly3-hexylthiophene:6,6-phenyl-C61-butyric-acid-methylester:Ag NP solar cells using photoinduced charge extraction with a linearly increasing voltage. We find that the addition of Ag NPs into the active layer significantly enhances carrier mobility but decreases the total extracted carrier. Atomic force microscopy shows that the Ag NPs tend to phase segregate from the organic material at high concentrations. This suggests that the enhanced mobility results from carriers traversing Ag NP subnetworks, and that the reduced carrier density results from increased recombination from carriers trapped on the Ag particles. © 2011 American Institute of Physics. doi:10.1063/1.3601742 Bulk heterojunction BHJ photovoltaics based on interpenetrating networks of electron-donating conjugated polymers and electron-accepting fullerenes continue to be the focus of substantial interest as a potentially inexpensive route to harvest solar energy. 1,2 Because organic materials suffer from low carrier mobilities, the active layers in BHJ devices tend to be quite thin 100 nm, which in turn can result in poor light absorption. As a result, conjugated polymer-based solar cells continue to have significantly lower efficiencies than their inorganic counterparts with the current record hovering around 8%. 3