研究実績の概要 |
For conductivity in perovskite materials, more general in ceramic materials, the grain boundaries play a major role. In this project, it could already be demonstrated that light above the band-gap can significantly increase the grain boundary conductivity. Thin films consisting 3mol% Gd doped CeO2 were compared, one epitaxial without grain boundaries, one polycrystalline with grain sizes around 50-100nm. Only in the polycrystalline film, the light increased the conductivity by a factor of around 3.5. That is an exceptional result. Further, a model was developed to explain the photo-effect on the ceramic material. For the characterization under light, two new measurement techniques have been adapted: intensity-modulated photocurrent spectoscopy (IMPS) and single-frequency impedance transients (SFIT). A publication summarizing the results, the methods and the model to explain the observed behavior has been submitted to Nature Materials and is currently in the second round of revisions. Furthermore, for perovskite materials as used in solar cells, new strategies for characterization have been developed based on electrochemical impedance spectroscopy. Measurements have been performed and the impact of interfaces is currently examined.
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