The Role of Higher Lying Electronic States in Charge Photogeneration in Organic Solar Cells |
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| Authors: | Giulia Grancini Maddalena Binda Stefanie Neutzner Luigino Criante Vittorio Sala Alberto Tagliaferri Guglielmo Lanzani |
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| Affiliation: | 1. Center for Nano Science and Technology@Polimi, Istituto Italiano di Tecnologia, Milan, Italy;2. Dipartimento di Fisica, Politecnico di Milano, Milan, Italy |
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| Abstract: | The role of excess photon energy on charge generation efficiency in bulk heterojunction solar cells is still an open issue for the organic photovoltaic community. Here, the spectral dependence of the internal quantum efficiency (IQE) for a poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)]:6,6‐phenyl‐C61‐butyric acid methyl ester (PCPDTBT:PC60BM)‐based solar cell is derived combining accurate optoelectronic characterization and comprehensive optical modeling. This joint approach is shown to be essential to get reliable values of the IQE. Photons with energy higher than the bandgap of the donor material can effectively contribute to enhance the IQE of the solar cell. This holds true independently of the device architecture, reflecting an intrinsic property of the active material. Moreover, the nanomorphology of the bulk heterojunction plays a crucial role in determining the IQE spectral dependence: the coarser and more crystalline, the lesser the gain in IQE upon high energy excitation. |
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| Keywords: | excess photon energy hot exciton dissociation internal quantum efficiencies optical modeling organic solar cells |
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