Identification and overcoming of loss mechanisms in nanostructured hybrid solar cells - pathways towards more efficient devices

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In the present work we want to explore the potential and the current limitations of nanostructured hybrid solar cells, where a periodic array of metal-oxide nanowires or nanotubes is used in combination with an organic semiconductor material. In principle, such network structures should lead to an improved performance and a better lifetime-stability compared to fully organic solar cells due to a more efficient charge separation and a higher stability of the metal oxides, respectively. However, up to now their efficiencies are lower than the ones of fully organic bulk-heterojunction cells. We want to explore the reasons for this. With the gained knowledge we will develop strategies to improve the performance. It is expected that the various interfaces which are occurring play a major role and we plan to investigate them on an atomic scale by advanced transmission electron microscopy methods. We will also study how the dimension, shape and crystallinity of the metal-oxide nanostructure effect the device performance. An important part will be the investigation of the device physics, especially charge generation, exciton separation, recombination and mobility. We will compare these values with standard bulk-heterojunction solar cells to emphasize the differences, which will enable us to identify and overcome current limitations of nanostructured hybrid solar cells.