The role of Ag nanoparticles in inverted polymer solar cells: Surface plasmon resonance and backscattering centers

Here, we demonstrate silver (Ag) nanoparticles (NPs) existing in molybdenum trioxide (MoO3) buffer layers can improve the photocurrent by surface plasmon resonance (SPR) and backscattering enhancement. The device structure is glass/indium tin oxides/titanium dioxide (TiO2)/regioregular poly(3-hexylthiophene):[6,6]-phenyl C-61 butyric acid methyl ester/MoO3/Ag NPs/MoO3/Ag. Compared to the device without Ag NPs, the short current density (J(sc)) is improved from 7.76 +/- 0.14 mA/cm(2) to 8.89 +/- 0.12 mA/cm(2), and the power conversion efficiency is also enhanced from 2.70%+/- 0.11% to 3.35%+/- 0.08%. The transmittance spectra show that the device with Ag NPs has weaker transmittance than the device without, which could be attributed to the photons absorption of Ag NPs and light scattering by Ag NPs. The absorption profile of the devices with or without Ag NPs is simulated using finite-difference time-domain methods. It is approved that the Ag NPs result in the absorption improvement by SPR and backscattering enhancement. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4798553]