|Wisnet, Andreas (2014): 1D TiO2 nanostructures probed by 2D transmission electron microscopy: while paving the way for their 3D reconstruction. Dissertation, LMU München: Faculty of Chemistry and Pharmacy|
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Hybrid solar cells based on nanoparticulate TiO2, dye and poly(3-hexylthiophene) are a common benchmark in the ﬁeld of solid-state dye-sensitized solar cells. One-dimensionally nanostructured titanium dioxide is expected to enhance power-conversion efficiency (PCE) due to a high surface area combined with a direct path for electrons from the active interface to the back electrode. However, current devices do not meet those expectations and cannot surpass their mesoporous counterparts. This work approaches the problem by detailed investigation of diverse nanostructures on a nanoscale by advanced transmission electron microscopy (TEM). Anodized TiO2 nanotubes are analyzed concerning their crystallinity. An unexpectedly large grain size is found, and its implication is shown by corresponding solar cell characteristics which feature an above-average fill factor. Quasi-single crystalline rutile nanowires are grown hydrothermally, and a peculiar defect structure consisting of free internal surfaces is revealed. A growth model based on Coulombic repulsion and steric hindrance is developed to explain the resulting V-shaped defect cascade. The inﬂuence of the defects on solar cell performance is investigated and interpreted by a combination of TEM, electronic device characterization and photoluminescence spectroscopy, including lifetime measurements. A speciﬁc annealing treatment is proposed to counter the defects, suppressing several loss mechanisms and resulting in an improvement of PCEs by 35 %. Simultaneously, a process is developed to streamline electron-tomographic reconstruction of complex nanoparticles. Its suitability is demonstrated by the reconstruction of a gold nanostar and a number of iron-based particles distributed on few-layered graphene.
|Item Type:||Thesis (Dissertation, LMU Munich)|
|Subjects:||600 Natural sciences and mathematics|
600 Natural sciences and mathematics > 540 Chemistry and allied sciences
|Faculties:||Faculty of Chemistry and Pharmacy|
|Date Accepted:||19. December 2014|
|1. Referee:||Scheu, Christina|
|Persistent Identifier (URN):||urn:nbn:de:bvb:19-179430|
|MD5 Checksum of the PDF-file:||d4391cc762eed4643f2f1f193708c27f|
|Signature of the printed copy:||0001/UMC 22711|
|Deposited On:||18. Feb 2015 15:17|
|Last Modified:||20. Jul 2016 10:38|
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