Improving the Efficiency of Bulk-heterojunction Solar Cells through Plasmonic Enhancement within a Silver Nanoparticle-Loaded Optical Spacer Layer.

We investigate the enhancement in the efficiency of organic bulk heterojunction solar cells enabled by plasmonic excitation of Ag nanoparticles (NPs) of different diameters (10, 20, and 30 nm), randomly incorporated within an optical spacing layer of TiO placed between the organic medium and the Ag cathode. Such structures significantly increase the optical absorption and the photocurrent within the device system, leading to a power conversion efficiency of more than 4%, over 2.5 times that of the control bulk heterojunction cell. This corresponds to a 61% increase in and a 6.3% in fill factor. 3D Finite-difference time-domain simulations were utilized to investigate the plasmonic field coupling within the nanogap medium of TiO. They show that coupling between the Ag nanoparticle and the Ag thin film cathode extends the wavelength range of the local field enhancement beyond that obtained for isolated NPs, providing a better overlap with the absorption spectrum of the organic medium.