Plasmonic absorption enhancement in organic solar cells with thin active layers

Abstract

The influence of silver nanoparticles on light absorption in organic solar cells based on poly(3-exylthiophene):(6,6)-phenyl-C61-butyric-acid-methyl ester is studied by means of finite element method simulations. The metallic nanoparticles are embedded directly inside the active layer. We investigate the enhancement mechanism and the influence of factors such as the spacing between neighboring nanoparticles, the particle diameter, and the coating thickness. The plasmonic resonance of the particles has a wideband influence on the absorption, and we observe a rich interaction between plasmonic enhancement and the absorption characteristics of the active layer material. An enhancement with a factor of around 1.56 is observed for nanoparticles with a diameter of 24 nm and a spacing of 40 nm, bringing the structure to the absorption level of much thicker active layers without nanoparticles. In addition, a significant effect of the particle coating thickness is observed.

Angle insensitive enhancement of organic solar cells using metallic gratings

“…Our refractive index data is obtained from ellipsometry measurements done at imec (Interuniversity Microelectronics Center, Leuven, Belgium). The refractive index data of the P3HT:PCBM blend is shown in [6]. Due to the periodic nature of the problem, only one period needs to be simulated by using the proper boundary conditions.…”

“…An example of the usage of silver square gratings to enhance silicon thin film solar cells is shown in recent publications [12,15]. Here, we explore the characteristics further and we examine specifically the angular behaviour of the excited modes for bulk heterojunction solar cells made of P3HT:PCBM (poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester) blends. The depth of the metallic grating is found to be crucial for a good wide-angle response for the case of normal triangular gratings.…”

“…In addition one can engineer the modes so that the absorption in the metal remains limited. Several metal geometries (gratings, particles [6][7][8][9]) and their locations in the cell (front, middle or back) are under active investigation for different types of solar cells. Plasmonic grating structures [5,[10][11][12][13][14][15] form a particularly interesting class, as they involve the patterning of an available metallic electrode.…”

Plasmonic excitation-assisted optical and electric enhancement in ultra-thin solar cells: the influence of nano-strip cross section

“…As the length of nano-strips along the z-direction is lager enough compared to their cross section, a two-dimensional (2D) numerical treatment is used. 13,54,55 Under this condition, the electromagnetic fields are dependent only to x and y. Accurate solutions for electric and magnetic field are obtained with considering proper boundary conditions and refractive index of materials.…”

Photonic crystal: energy-related applications

“…Metallic nanoparticle-based schemes 57,58 can provide polarization-insensitive enhancement, but they do not offer conductive pathways and cannot replace ITO electrodes. Metallic grating-based designs 11,59 do provide an alternative to ITO electrodes.…”