Angle insensitive enhancement of organic solar cells using metallic gratings

We explore the optical enhancement of organic photovoltaic cells by incorporating a metallic grating as the back contact. We numerically demonstrate a strongly enhanced light absorption exploiting a complex interplay between multiple electromagnetic wave phenomena, among which surface plasmon polariton (SPP) resonances, waveguide mode resonances, Fabry-Perot modes, and scattering. We focus on a triangular grating structure and describe the particular opportunities to obtain a good angular performance. In addition we introduce a novel multiperiodic geometry that incorporates multiple types of SPP resonances. Our triangular structure shows an increased absorption of 15.6% with the AM1.5G spectrum in the 300-800 nm wavelength range. For the multiperiodic grating case a significant further increase to 20.7% is shown. (C) 2011 American Institute of Physics. [doi:10.1063/1.3533980]