Light trapping plasmonic butterfly-wing-shaped nanostructures for enhanced absorption and efficiency in organic solar cells

Abstract

This paper presents organic solar cells (OSCs) containing a one-dimensional (1D) periodic array of plasmonic butterfly-wing-shaped nanostructures, where silver butterfly-wing-shaped nanostructures are present in the back region of the active medium poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl]] with [6,6]-phenyl-C71-butric acid methyl ester. Finite-difference time-domain (FDTD) modeling was employed to simulate the interaction of light with the plasmonic nanostructures, and it was demonstrated that these plasmonic nanostructures lead to a broadband enhancement of light absorption in the active medium. These plasmonic nanostructures lead to enhanced scattering and trapping of the incident optical radiation at multiple wavelengths due to surface plasmon excitation at these wavelengths. This enhanced scattering leads to an increased path length of light, as well as an enhanced intensity of the overall electric field in the active layer of the OSC, which further leads to an increase in absorption. The plasmonic butterfly-wing-shaped nanostructures-containing solar cells were also simulated with indium tin oxide (ITO) nanogratings (NGs) placed on the top surface of the solar cells. It was seen that the presence of the ITO NGs leads to a further enhancement in absorption. In these OSCs containing both the plasmonic butterfly-wing-shaped nanostructures and the ITO NGs, the highest values of enhancements in the absorption and cell efficiency were calculated to be ∼20% and ∼25%, respectively.