Plasmonic Backscattering Effect in High‐Efficient Organic Photovoltaic Devices |
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Authors: | George Kakavelakis Ioannis Vangelidis Amelie Heuer‐Jungemann Antonios G. Kanaras Elefterios Lidorikis Emmanuel Stratakis Emmanuel Kymakis |
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Affiliation: | 1. Center of Materials Technology and Photonics & Electrical Engineering Department, Technological Educational Institute (TEI) of Crete, Heraklion, Crete, Greece;2. Department of Materials Science and Technology, University of Crete, Heraklion, Crete, Greece;3. Department of Materials Science and Engineering, University of Ioannina, Ioannina, Greece;4. Physics and Astronomy, Faculty of Physical Sciences and Engineering, University of Southampton, Southampton, UK;5. Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Heraklion Crete, Greece |
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Abstract: | A universal strategy for efficient light trapping through the incorporation of gold nanorods on the electron transport layer (rear) of organic photovoltaic devices is demonstrated. Utilizing the photons that are transmitted through the active layer of a bulk heterojunction photovoltaic device and would otherwise be lost, a significant enhancement in power conversion efficiency (PCE) of poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)]:phenyl‐C71‐butyric acid methyl ester (PCDTBT:PC71BM) and poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b] thiophenediyl]] (PTB7):PC71BM by ≈13% and ≈8%, respectively. PCEs over 8% are reported for devices based on the PTB7:PC71BM blend. A comprehensive optical and electrical characterization of our devices to clarify the influence of gold nanorods on exciton generation, dissociation, charge recombination, and transport inside the thin film devices is performed. By correlating the experimental data with detailed numerical simulations, the near‐field and far‐field scattering effects are separated of gold nanorods (Au NRs), and confidently attribute part of the performance enhancement to the enhanced absorption caused by backscattering. While, a secondary contribution from the Au NRs that partially protrude inside the active layer and exhibit strong near‐fields due to localized surface plasmon resonance effects is also observed but is minor in magnitude. Furthermore, another important contribution to the enhanced performance is electrical in nature and comes from the increased charge collection probability. |
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Keywords: | efficient light scattering finite‐difference time‐domain optical simulation gold nanorod organic photovoltaic surface plasmon resonance |
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