Surface plasmon polariton assisted organic solar cells
We propose a lateral tandem cell system consisting of organic thin-film photovoltaic devices. The crucial element of the system is a surface plasmon polariton (SPP) assisted organic solar cell employing a metallic grating electrode. In the SPP-assisted solar cell, the incident light resonantly excites an SPP mode to increase the optical field intensity in the absorption layer. As a result, a high absorption efficiency is maintained when the thickness of the absorption layer is decreased below the exciton diffusion length, thereby overcoming the 'exciton diffusion bottleneck' present in conventional organic solar cells. For a model structure, where an organic multilayer is sandwiched by a planar cathode and a grating anode, both consisting of Ag, we show, using the finite element method, that the absorption efficiency of a 10-nm-thick absorption layer with the absorption coefficient of 105 cm -1 exceeds 80% for TM-polarized incident light with a wavelength of 765 nm. We show that the resonance can be tuned by varying the grating period. We also discuss design guidelines for the lateral tandem cell system, and estimate its performance.
