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Three-dimensional cavity nanoantenna coupled plasmonic nanodots for ultrahigh and uniform surface-enhanced Raman scattering over large area

Author(s): Li, W-D; Chou, Stephen Y

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Abstract: Three of central challenges in solar cells are high light coupling into solar cell, high light trapping and absorption in a sub-absorptionlength- thick active layer, and replacement of the indium-tin-oxide (ITO) transparent electrode used in thin-film devices. Here, we report a proposal and the first experimental study and demonstration of a new ultra-thin highefficiency organic solar cell (SC), termed “plasmonic cavity with subwavelength hole-array (PlaCSH) solar cell”, that offers a solution to all three issues with unprecedented performances. The ultrathin PlaCSH-SC is a thin plasmonic cavity that consists of a 30 nm thick front metal–mesh electrode with subwavelength hole–array (MESH) which replaces ITO, a thin (100 nm thick) back metal electrode, and in-between a polymer photovoltaic active layer (P3HT/PCBM) of 85 nm thick (1/3 average absorption-length). Experimentally, the PlaCSH-SCs have achieved (1) light coupling–efficiency/absorptance as high as 96% (average 90%), broadband, and Omni acceptance (light coupling nearly independent of both light incident angle and polarization); (2) an external quantum efficiency of 69% for only 27% single-pass active layer absorptance; leading to (3) a 4.4% power conversion efficiency (PCE) at standard–solar–irradiation, which is 52% higher than the reference ITO-SC (identical structure and fabrication to PlaCSH-SC except MESH replaced by ITO), and also is among the highest PCE for the material system that was achievable previously only by using thick active materials and/or optimized polymer compositions and treatments. In harvesting scattered light, the Omni acceptance can increase PCE by additional 81% over ITO-SC, leading to a total 175% increase (i.e. 8% PCE). Furthermore, we found that (a) after formation of PlaCSH the light reflection and absorption by MESH are reduced by 2 to 6 fold from the values when it is alone; and (b) the sheet resistance of a 30 nm thick MESH is 2.2 ohm/sq or less–4.5 fold or more lower than the best reported value for a 100 nm thick ITO film, giving a lowest reflectance-sheetresistance product. Finally, fabrication of PlaCSH has used nanoimprint on 4” wafer and is scalable to roll-to-roll manufacturing. The designs, fabrications, and findings are applicable to thin solar cells in other materials.
Publication Date: 28-Nov-2012
Electronic Publication Date: 14-Jan-2013
Citation: Li, W-D, Ding, F, Hu, J, Chou, SY. (2011). Three-dimensional cavity nanoantenna coupled plasmonic nanodots for ultrahigh and uniform surface-enhanced Raman scattering over large area. Optics Express, 19 (3925 - 3936. doi:10.1364/OE.19.003925
DOI: doi:10.1364/OE.19.003925
Pages: 3925 - 3936
Type of Material: Journal Article
Journal/Proceeding Title: Optics Express
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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