Enhancement of optical absorption in thin-film solar cells through the excitation of higher-order nanoparticle plasmon modes.

Advanced Photonics and Plasmonics Group, Institute of High Performance Computing, Singapore.
Optics Express (Impact Factor: 3.53). 07/2009; 17(12):10195-205. DOI: 10.1364/OE.17.010195
Source: PubMed

ABSTRACT Recent research in the rapidly emerging field of plasmonics has shown the potential to significantly enhance light trapping inside thin-film solar cells by using metallic nanoparticles. In this article it is demonstrated the plasmon enhancement of optical absorption in amorphous silicon solar cells by using silver nanoparticles. Based on the analysis of the higher-order surface plasmon modes, it is shown how spectral positions of the surface plasmons affect the plasmonic enhancement of thin-film solar cells. By using the predictive 3D modeling, we investigate the effect of the higher-order modes on that enhancement. Finally, we suggest how to maximize the light trapping and optical absorption in the thin-film cell by optimizing the nanoparticle array parameters, which in turn can be used to fine tune the corresponding surface plasmon modes.

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    ABSTRACT: A high-absorption of thin film system used for solar energy photon-thermal conversion is designed. Which is composed of four function parts with metals and dielectric materials. The result of design show that it has a very high absorption over 95% with wide working wavelength range from 400nm to 1000nm and incident angle from 0o to 60o.
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    ABSTRACT: Plasmonic effects associated with localized surface plasmon (LSP) resonances such as strong light trapping, large scattering cross-section, and giant electric field enhancement have received much attention for the more efficient harvesting of solar energy. Notably, even as the thickness of the active layer is significantly reduced, the optical absorption capability of a solar cell could be maintained with the incorporation of plasmonic effects. This is especially important for the development of bulk heterojunction (BHJ) organic solar cells (OSCs), where the short exciton diffusion length, low carrier mobility, and strong charge recombination in organic materials strongly favors the use of optically thin active layers (<100 nm). However, the disappointing performance improvements obtained with plasmonic effects in the majority of BHJ OSCs realized to date suggests that plasmonic effects are yet to be fully taken advantage of; for example, in thick active layer OSCs (>100 nm), the optical absorption is already high, even in the absence of plasmonic effects, while in thin active layer OSCs (<100 nm), insufficient attention has been given to the analysis of plasmonic effects, such as the impact of plasmonic nanoparticle (NP) geometrical factors on the directional scattering efficiency. In this paper, we propose and demonstrate that the geometrical tuning of spheroidal plasmonic nanoparticles (NPs) could enable the full exploitation of plasmonic effects, providing dramatic improvements to the light absorption and energy harvesting capability of ultrathin film BHJ OSCs. Our theoretical analysis demonstrates a dramatic enhancement in optical absorption of ∼60% with spheroidal NPs embedded in a BHJ OSC device with ultrathin, <100 nm active layer, as compared to an NP absent reference device. These improvements are explained according to enhanced scattering of light into the active layer plane, spectral broadening of absorption resonances, in addition to an increased plasmonic modal volume, exhibited near LSP resonances of spheroidal NPs with optimal eccentricity. The result of our coupled optical-electrical device simulations also proves that the outstanding optical absorption enhancement obtained from the proposed device indeed translates into significant electrical performance gains; such as a ∼30% increase in the short-circuit current and ∼20% improvement in the power conversion efficiency (PCE). B ulk heterojunction organic solar cells with active layers comprising regioregular mixtures of polymer donor and fullerene acceptor materials have been envisioned as a promising next generation energy harvesting device due to their lightweight, mechanical robustness, and low-cost, all-solution processing and fabrication. 1−6 Nonetheless, currently inhibiting the wide scale emergence of BHJ OSCs is the poor carrier mobility and short exciton diffusion length in organic semiconductors that restricts their active layer to very small thicknesses, greatly diminishing their optical absorption and power conversion efficiency (PCE) to well below that of their inorganic counterparts (e.g., those based on Si, GaAs, CdTe, Cu(In, Ga)Se 2 , etc.). Efforts to address this issue have been thrust in two main directions. One of these emphasizes improvement of the constituent materials and their morphological implementation, such as development of new donor/ acceptor organic materials 7−11 or the introduction of efficient hole/electron transport layers via new process/postfabrication treatments, 11−13 and numerous morphological optimizations 2−5,14,15 (e.g., advanced heterojunction structure and blend network). The other main direction has been toward improving the optical absorption capability of the device, especially in the active layer, through the introduction of plasmonic effects utilizing the strong field localization and scattering of metallic nanostructures. For example, localized surface plasmon (LSP) resonances supported by metallic gratings, 16,17,33 nanostructures, 18,19 and nanoparticles
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