Enhancement of optical absorption in thin-film organic solar cells through the excitation of plasmonic modes in metallic gratings

Abstract

We theoretically investigate the enhancement of optical absorption in thin-film organic solar cells in which the top transparent electrode is partially substituted by a periodic metallic grating. We show that the grating can result in broadband optical absorption enhancement for TM-polarized light, due to the large field enhancement in the vicinity of the strips of the grating, associated with the excitation of plasmonic modes. The overall optical absorption in the organic layers can be greatly enhanced up to ∼50% for such solar cell structures.

Volumetric plasmonic resonators for very thin organic solar cells

“…To address this problem, there has been an increasing interest in designing plasmonic structures around the active layers for enhancing their total optical absorption. Using a single layer of such plasmonic structures either on the top or at the bottom of these absorbing layers has been extensively studied in the literature 1,2,3 . In this work, different than the previous reports, we focus on a new design concept of volumetric plasmonic resonators that relies on the idea of coupling two (or more) layers of coupled plasmonic structures embedded in the organic solar cells.…”

Volumetric plasmonic resonator architecture for thin-film solar cells

“…The resulted absorption enhancement levels reported for such single layers have typically been limited within the range of ϳ18% -50%, when considering both transverse-magnetic ͑TM͒ and transverse-electric ͑TE͒ polarizations. 8,9,12,13 Therefore, there is a need for further extending field localization across the volume of the active materials to contribute to increasing field localization and enhancing photon absorption efficiency in thin-film solar cells, beyond the improvement levels obtained using individual plasmonic layers. This, however, requires innovative designs.…”

“…But these use only a single nanopatterned layer of plasmonic structures, which limits the full utilization of the volume of the active material. All of these previous designs were based on placing the metal layer either only on the top 3,[7][8][9][10]15 or only at the bottom 3,[11][12][13][14] of the active layers for exciting their plasmon modes. The resulted absorption enhancement levels reported for such single layers have typically been limited within the range of ϳ18% -50%, when considering both transverse-magnetic ͑TM͒ and transverse-electric ͑TE͒ polarizations.…”

“…In these numerical simulations, we calculated the frequency domain response by taking the Fourier transform of time domain representations. This computational approach allowed us to use experimental refractive index data to represent the device materials including CuPc, 8 PTCBl, 8 Ag, 16 and BCP 17 in our structures. In all simulations, reflection from the air/glass interface was omitted.…”

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] These prior studies used either randomly distributed metal nanoparticles 3,6,7 or nanopatterned metal layers. 3,[8][9][10][11][12][13][14] Although such metal nanoparticles can be conveniently blended across the active layers, they suffer from random distribution in the active material and limited spatial control. On the other hand, the metal layers can be nanostructured with precision.…”