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Photochemical Transformations in Fullerene and Molybdenum Oxide Affect the Stability of Bilayer Organic Solar Cells |
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| Authors: | Hui Zhang Andreas Borgschulte Fernando A. Castro Rowena Crockett Andreas C. Gerecke Okan Deniz Jakob Heier Sandra Jenatsch Frank Nüesch Carlos Sanchez‐Sanchez Alina Zoladek‐Lemanczyk Roland Hany |
| Affiliation: | 1. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Functional Polymers, Dübendorf, Switzerland;2. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Hydrogen and Energy, Dübendorf, Switzerland;3. NPL, National Physical Laboratory, Materials Division, Teddington, UK;4. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Nanoscale Materials Science, Dübendorf, Switzerland;5. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Analytical Chemistry, Dübendorf, Switzerland;6. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory nanotech@surfaces, Dübendorf, Switzerland;7. Institut des Matériaux, Ecole Polytechnique Fédéral de Lausanne, Lausanne, Switzerland |
| Abstract: | Thin films of fullerene C60 and molybdenum oxide (MoO3) are ubiquitously used as the electron acceptor material and hole extraction interfacial layer for the fabrication of organic photovoltaic (OPV) cells. It is well known that light exposure induces color changes in MoO3 (photochromism) and the formation of intermolecular bonds between C60 molecules (photopolymerization). The influence of these photoinduced reactions on the long‐term stability of OPV cells, however, has not previously been studied in detail. Here, a study and discussion of the early (<5 days) aging mechanisms occurring in illuminated ITO/MoO3/organic cyanine dye/C60/Alq3/Ag bilayer solar cells under nitrogen atmosphere is presented. A degradation process at the organic heterojunction is identified and the formation of Mo5+ species during illumination is found to adversely affect cell behavior. For these widely used materials, the results suggest that light processing is a first necessary step before OPV characteristics can be meaningfully rated. |
| Keywords: | fullerenes molybdenum oxide photopolymerization photochromism organic solar cells |