Materials and device concepts for renewable solar hydrogen production, and size dependent properties of ZnO quantum dots are the two main themes of this thesis. ZnO particles with diameters less than 10 nm, which are small enough for electronic quantum confinement, were synthesized by hydrolysis in alkaline zinc acetate solutions. Properties investigated include: the band gap - particle size relation, phonon quantum confinement, visible and UV-fluorescence as well as photocatalytic performance. In order to determine the absolute energetic position of the band edges and the position of trap levels involved in the visible fluorescence, methods based on combining linear sweep voltammetry and optical measurements were developed. The large band gap of ZnO prevents absorption of visible light, and in order to construct devices capable of utilizing a larger part of the solar spectrum, other materials were also investigated, like hematite , Fe2O3, and CIGS, CuIn1-xGaxSe2. The optical properties of hematite were investigated as a function of film thickness on films deposited by ALD. For films thinner than 20 nm, a blue shift was observed for both the absorption maximum, the indirect band gap as well as for the direct transitions. The probability for the indirect transition decreased substantially for thinner films due to a suppressed photon/phonon coupling. These effects decrease the visible absorption for films thin enough for effective charge transport in photocatalytic applications. CIGS was demonstrated to be a highly interesting material for solar hydrogen production. CIGS based photocathodes demonstrated high photocurrents for the hydrogen evolution half reaction. The electrode stability was problematic, but was solved by introducing a modular approach based on spatial separation of the basic functionalities in the device. To construct devices capable of driving the full reaction, the possibility to use cells interconnected in series as an alternative to tandem devices were investigated. A stable, monolithic device based on three CIGS cells interconnected in series, reaching beyond 10 % STH-efficiency, was finally demonstrated. With experimental support from the CIGS-devices, the entire process of solar hydrogen production was reviewed with respect to the underlying physical processes, with special focus on the similarities and differences between various device concepts.

La littérature récente en commerce international et macroéconomie a souligné le rôle majeur de grandes firmes dans les résultats agrégés d'une économie. Les grandes firmes influencent, inter alia, les fluctuations économiques, les performances à l'exportation et les inégalités de salaires et de coût de la vie. Il est donc crucial de saisir comment les grandes firmes émergent et se comportent. Cette thèse s'intéresse à trois aspects de cette question. Premièrement, j'étudie comment les firmes ajustent la qualité de leurs produits à une intensification de la compétition "low-cost" sur les marchés étrangers. Pour ce faire, je développe une nouvelle méthode d'estimation de la qualité des produits au niveau firme et je trouve que les firmes augmentent leur qualité en réponse à la compétition "low-cost". Deuxièmement, j'examine la manière dont les firmes ajustent leurs ventes lorsqu'un choc de demande (e.g., une récession) frappe une de leurs destinations. Dans le cadre de l'industrie du Champagne durant la récession de 2000-2001, je montre que les firmes ré-allouent leurs ventes vers les marchés dont les conditions de demandes sont plus favorables. Cela suggère un nouveau mécanisme de diffusion internationale des chocs. Finalement, je regarde la manière dont les firmes ajustent leur taille et leur mix de capital et travail lorsque la régulation du travail contraint plus fortement les grandes firmes. Dans le cas du seuil de 50 employés en France, je trouve que les firmes se contractent et substituent du travail au capital pour limiter le coût de la régulation. Au niveau macro, mes résultats suggèrent que la régulation profite aux travailleurs mais pas aux détenteurs de capital. / Recent literature in international economics and macroeconomics has pointed to the major role played by large firms in shaping aggregate economic outcomes. Large firms influence, inter alia, economic fluctuations, performance on export markets and inequalities between workers and between consumers. It is therefore crucial to understand how large firms emerge and behave. In the present thesis, I look at three independent aspects of this question. First, I study how exporting firms adjust the quality of the products they export in response to an intensification of "low-cost" competition in foreign markets. To this end, I develop a new method to estimate the quality of products at the firm-level and I find evidence that firms upgrade quality in response to "low-cost" competition. Second, I investigate the way exporting firms adjust their sales when a demand shock (e.g. an economic recession, a war) occurs in one of their destinations. In the context of the Champagne wine industry during the 2000-2001 economic recession, I show that firms reallocate their sales toward markets where demand conditions are relatively more favorable. Lastly, I look at the way firms adjust their size and their mix of capital and labor in response to labor regulations which are more binding to large firms. I find that firms shrink and substitute capital for labor to mitigate the labor cost of the regulation. At the aggregate level, preliminary results suggests that workers gain from the regulation while capital owners lose.

No description available.

This study investigates size-selective predation of four groups predaceous aquatic insects: adults and larvae of diving beetles (Dytiscidae), larvae of dragonflies (Odonata) and aquatic true bugs (Heteroptera) using laboratory feeding experiments and relates the results to morphometric data obtained for each predator.

No description available.

京都大学 / 新制・課程博士 / 博士(人間・環境学) / 甲第24693号 / 人博第1066号 / 新制||人||250(附属図書館) / 2022||人博||1066(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 吉田 寿雄, 教授 田部 勢津久, 教授 中村 敏浩, 教授 寺村 謙太郎 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

We developed a three-step colloidal synthesis of near-infrared active Cu-In-Se (CISe)/ZnS core/shell nanocrystals (NCs) via a sequential partial cation exchange. In the first step binary highly copper deficient Cu2‒xSe NCs were synthesized, followed by a partial cation exchange of copper to indium ions yielding CISe NCs. In order to enhance the stability and the photoluminescence (PL) properties of the NCs, a subsequent ZnS shell was grown, resulting in CISe/ZnS core/shell NCs. These core/shell hetero-NCs exhibited a dramatic increase in size and a restructuring to trigonal pyramidal particles. The reaction parameters, e.g. the Cu:Se-ratio, the temperature and the time were carefully tuned enabling a distinct control over the size and the composition of the NCs. By varying only the size of the CISe/ZnS NCs (from 9 to 18 nm) the PL spectra could be tuned covering a wide range with maxima from 990 nm to 1210 nm. Thus, in these experiments we demonstrate a clear dependence of the optical properties of these materials on their size and extend the PL range of CISe-based nanoparticles further to the infrared part of the spectrum. Furthermore, the relatively large size of these NCs allows their detailed structural analysis via electron microscopy techniques, which is particularly challenging in the case of small particles and especially important to relate the size, composition and crystal structure to their optoelectronic properties.