Effect of embedded nanoparticle surface chemistry on plasmonic organic photovoltaic devices

Abstract

The effect of noble metal nanoparticle (NP) synthesis method on the plasmonic enhancement of organic photovoltaic device performance by these NPs is reviewed. For direct incorporation into a polymer fullerene bulk heterojunction (BHJ) active layer, chemically synthesized colloidal Au or Ag NPs with organic ligands are generally ineffective. Due to the tendency of the ligands in causing exciton quenching, carrier trapping and recombination, the device power conversion efficiency (PCE) can be lower than a BHJ device without NPs. Ligand-free metal NPs prepared by physical methods such as pulsed laser ablation and electron beam evaporation can enhance the PCE when introduced into the BHJ. An alternative effective approach for both polymer and small molecule BHJ devices is core shell metal–silica NPs. Regardless of synthesis method, the NP size should be controlled to the range of ~50–100 nm to increase light trapping due to scattering and achieve synergistic enhancement. A non-spherical NP morphology with tunable dual localized surface plasmon resonance peaks at visible wavelengths is highly desirable. For core shell metal–silica NPs, the dielectric shell thickness must be optimized to ensure significant localized field enhancement at the surface of the NP.