Characterization & Modification of Copper and Iron Oxide Nanoparticles for Application as Absorber Material in Silicon based Thin Film Solar Cells

Beschreibung

The present thesis deals with the characterization and modication of semiconducting copper oxide (CuO, Cu2O) and iron oxide ( -Fe2O3, -Fe2O3) nanoparticles, which provide a basis for an innovative solar cell concept involving nanoparticles composed of almost unlimitedly available elements as absorber material in thin lm 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 lms. 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 in uence 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 de ection 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 (Cu2O) is expected and observed after annealing at 800 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 C and 1000 C. Analyzing selected Raman and PDS spectra of the nanoparticles annealed at 800 C, the volume fraction of a remaining tenorite phase is estimated to be smaller than 20%. There is no indication for the presence of tenorite after annealing at 1000 C. In comparison to results reported for tenorite bulk material and thin lms, nanoparticles include fewer defects and therefore show superior opto-electronic properties. The cuprite nanoparticles exhibit excellent properties at least similar to high quality single crystals. In contrast to results usually reported in the literature for cuprite thin lms, the PL spectra are not dominated by strongly pronounced defect emission, which conrms that high quality nanoparticles can be easier prepared than corresponding thin lms

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Maurice René Nuys

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Copper Oxide Raman spectroscopy XRD

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