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Title Roll-to-Roll Processing of Polymer Solar Cells
Author Lilliedal, Mathilde Raad (Solar Energy Programme, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Supervisor Krebs, Frederik C (Solar Energy Programme, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2010
Abstract Flexible roll to roll processed polymer solar cells are interesting as a renewable energy technology that is easily producible and hold promise of high and stable energy conversion efficiency. Phenomena that lead to low efficiency cells, expressed as inflection points in IV-curves, and photo-annealing processes, which result in removal of the inflection point, are investigated. The goal is to optimize the characterization of devices and obtain freshly produced cells with maximum efficiency. A large series of roll to roll produced modules (consisting of 8 series connected cells) with the layer structure: PET-ITO-ZnO-P3HT:PCBM-PEDOT:PSS-Ag were fabricated using a combination of slot-die coating and screen printing; they were then encapsulated using a polymer based barrier material. All manufacturing steps were carried out in ambient air. All modules showed a consistent initial inflection point in IV-curves with corresponding poor performance. Photo-annealing over time with illumination of 1000 W∙m-2 at 85 oC resulted in gradual removal of the inflection point and increase in performance. The dynamic nature of the photo-annealing process was observed as the inflection point re-appeared upon dark storage. The characteristics and stability of the photo-annealing process was further investigated by studying the effects of several key factors: temperature, illumination, and atmosphere. In order to study possible interface barriers and processes related to inflection points and photo-annealing, adhesion tests and chemical analyses of intrinsic surfaces were carried out. It is concluded that the photoconductivity of the semiconducting ZnO plays an important role in the appearance of the inflection point. It is very likely that processes such as ZnO promoted photooxidation of organics and UV induced desorption of oxygen from the ZnO surface affect the photo-annealing process. Redistribution of oxygen inside the cell and chemical adsorption of oxygen could lead to the observed re-appearance of the inflection point. It is anticipated that the findings are applicable to various other cell structures based on semiconducting oxides and that findings may have influences on the possibilities and scale-up of polymer solar technologies.
Imprint Risø National Laboratory for Sustainable Energy : Roskilde
Pages 63
Keywords Solenergi; Solar energy; Plastsolceller; Polymer solar cells
Fulltext
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Admin Creation date: 2010-05-12    Update date: 2010-05-12    Source: dtu    ID: 262054    Original MXD