Abstract
The increasing need for energy can be satisfied by harvesting energy directly from sunlight; organic photovoltaics (OPVs) offer the possibility to do so in a cheap and sustainable way. This thesis deals with the physics of organic solar cells, providing insight into the mechanisms that limits the performance and the stability of the devices.
The efficiency of organic solar cells based on the blend of a conjugated polymer (donor) and a fullerene derivative (acceptor) is very sensitive to the morphology of the active layer. The first part of the thesis aims at establishing a quantitative relation between morphology and efficiency. The electronic properties and the morphology of several organic solar cells are experimentally characterized; the results are then used as input parameters for a model that calculates the current extracted from the solar cell.
Next, it is shown how the ratio of recombination and extraction rates of charge carriers determines the fill factor (FF) of organic solar cell. FF is one of the parameters that characterize the efficiency of a solar cell. In this thesis is explained why the FF of organic solar cells changes so much with active layer thickness, light intensity and material properties.
Finally, attention is given to the stability of polymer:fullerene blends. In particular, the UV-induced degradation of PTB7:[70]PCBM blends in inert atmosphere is studied. It is shown that upon UV exposure the transport of electrons is deteriorated, and that this degradation occurs only if both the materials are exposed to UV.
The efficiency of organic solar cells based on the blend of a conjugated polymer (donor) and a fullerene derivative (acceptor) is very sensitive to the morphology of the active layer. The first part of the thesis aims at establishing a quantitative relation between morphology and efficiency. The electronic properties and the morphology of several organic solar cells are experimentally characterized; the results are then used as input parameters for a model that calculates the current extracted from the solar cell.
Next, it is shown how the ratio of recombination and extraction rates of charge carriers determines the fill factor (FF) of organic solar cell. FF is one of the parameters that characterize the efficiency of a solar cell. In this thesis is explained why the FF of organic solar cells changes so much with active layer thickness, light intensity and material properties.
Finally, attention is given to the stability of polymer:fullerene blends. In particular, the UV-induced degradation of PTB7:[70]PCBM blends in inert atmosphere is studied. It is shown that upon UV exposure the transport of electrons is deteriorated, and that this degradation occurs only if both the materials are exposed to UV.
| Original language | English |
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| Qualification | Doctor of Philosophy |
| Awarding Institution |
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| Supervisors/Advisors |
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| Award date | 26-Feb-2016 |
| Place of Publication | [Groningen] |
| Publisher | |
| Print ISBNs | 978-90-367-8582-2 |
| Electronic ISBNs | 978-90-367-8583-9 |
| Publication status | Published - 2016 |