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| Home > Workflow collections > Public records > Characterization & Modification of Copper and Iron Oxide Nanoparticles for Application as Absorber Material in Silicon based Thin Film Solar Cells |
| Book/Dissertation / PhD Thesis | FZJ-2015-06605 |
2015
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-096-8
Please use a persistent id in citations: http://hdl.handle.net/2128/9429 urn:nbn:de:0001-2016022919
Abstract: The present thesis deals with the characterization and modication of semiconductingcopper oxide (CuO, Cu$_{2}$O) and iron oxide ($\gamma$-Fe$_{2}$O$_{3}$, $\alpha$-Fe$_{2}$O$_{3}$) nanoparticles, which provide a basis for an innovative solar cell concept involving nanoparticles composed of almost unlimitedly available elements as absorber material in thin film solar cells. This approach is promising to meet the requirements of increasing the production capacity and lowering the production costs if the nanoparticles exhibit superior properties compared to corresponding thin films. Therefore, the goal of this thesis is to demonstrate the high quality of semiconducting nanoparticles that can be achieved by proper treatment. The structural and opto-electronic properties of copper as well as iron oxide compounds are investigated and the inuence of thermal annealing is analyzed. Commercially available tenorite (CuO) nanoparticles with a diameter of about 30nm are annealed stepwise up to 1000 C in air and nitrogen atmosphere. The photoluminescence (PL) and photothermal deflection spectroscopy (PDS) results show tenorite band emission at about 1.3 eV, which strongly increases accompanied by a decreasing sub gap absorption with increasing annealing temperature up to 700 C and 1000 C in nitrogen atmosphere and air, respectively. These variations are ascribed to a reduction of the defect concentration. According to literature, a phase transition from tenorite to cuprite (Cu$_{2}$O) is expected and observed after annealing at 800 $^{\circ}$C in nitrogen atmosphere. Strong cuprite band edge emission at about 2 eV accompanied by very weak defect and possibly tenorite band edge emission is found for the samples annealed at 800 $^{\circ}$C and 1000 $^{\circ}$C. Analyzing selected Raman and PDS spectra of the nanoparticles annealed at 800 $^{\circ}$C, the volume fraction of a remaining tenorite phase is estimated to be smaller than 20%. There is noindication for the presence of tenorite after annealing at 1000 $^{\circ}$C. In comparison to results reported for tenorite bulk material and thin films, nanoparticlesinclude fewer defects and therefore show superior opto-electronic properties. The cuprite nanoparticles exhibit excellent properties at least similar to high qualitysingle crystals. In contrast to results usually reported in the literature for cuprite thin films, the PL spectra are not dominated by strongly pronounced defect emission,which confirms that high quality nanoparticles can be easier prepared than corresponding thin films. Likewise, commercially available maghemite ($\gamma$-Fe$_{2}$O$_{3}$) nanoparticles with a diameter of about 8nm to 15 nm are modified by oven annealing in nitrogen atmosphere up to 900 $^{\circ}$C. The PDS and PL results of as-prepared nanoparticles indicate the band gap at about 2 eV and a weakly pronounced and broad emission in the spectral regionof the band gap. Up to an annealing temperature of 450 $^{\circ}$C, the nanoparticles remain in the maghemite phase and their opto-electronic properties are only weakly affected. The PDS spectra reveal typical absorption features that are ascribed to ligand field transitions at about 1.4 eV and 1.9 eV. After further annealing at 550 $^{\circ}$C, [...]
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