Perylene Sensitization of Fullerenes for Improved Performance in Organic Photovoltaics |
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Authors: | Holger C Hesse Jonas Weickert Christian Hundschell Xinliang Feng Klaus Müllen Bert Nickel Attila J Mozer Lukas Schmidt‐Mende |
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Institution: | 1. Dept. of Physics and Center for NanoScience (CeNS), Amalienstr. 54, 80799, München, Germany;2. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany;3. Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Wollongong 2522, Australia |
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Abstract: | We present the addition of an energy relay dye to fullerenes resulting in increased light harvesting and significantly improved power conversion efficiency for organic photovoltaic (OPV) devices. Although exhibiting excellent properties as electron acceptors, visible light absorption of fullerenes is limited. Strongly light absorbing donor materials are needed for efficient light harvesting in the thin active layer of OPV devices. Therefore, photocurrent generation and thus power conversion efficiency of this type of solar cell is confined by the overlap of the relatively narrow absorption band of commonly used donor molecules with the solar spectrum. Herein the concept of fullerene dye sensitization is presented, which allows increased light harvesting on the electron acceptor side of the heterojunction. The concept is exemplarily shown for an UV absorbing small molecule and a near infrared absorbing polymer, namely hexa‐peri‐hexabenzocoronene (HBC) and Poly2,1,3‐benzothiadiazole‐4,7‐diyl4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta2,1‐b:3,4‐b']dithiophene‐2,6‐diyl]] (PCPDTBT), respectively. In both systems remarkably higher power conversion efficiency is achieved via perylene sensitization of the fullerene acceptor. Steady state photoluminescence, transient absorption and transient photocurrent decay studies reveal pathways of the additionally generated excited states at the sensitizer molecule. The findings suggest fluorescence resonance energy transfer from the photo‐excited dye to the fullerene enabling decoupling of light absorption and charge transport. The presented sensitization method is proposed as a viable new concept for performance enhancement in organic photovoltaic devices. |
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Keywords: | dye‐sensitization fullerenes organic electronics photovoltaic devices solar cells |
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