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Renewable energy sources, in particular, photovoltaic solar cells and hydrogen fuel, are expected to be the pillars of a sustainable society. Chalcopyrite CuGaSe2 (CGSe) has potential for using in such applications. This article presents efficient solar cells suitable as top cells for tandem devices and highly active photocathodes for solar hydrogen evolution using CGSe photoabsorber layers with modified p–n heterointerfaces. Rb‐doping during the last stage of CGSe film growth effectively improves the photovoltaic performance, and solar cell efficiency of >10% with a high fill factor (FF) of 74.6% is obtained. The half‐cell solar‐to‐hydrogen conversion efficiency reaches 8% with the use of a photocathode composed of a CGSe film grown in an identical growth batch. Interface modification with i) a Cu‐deficient layer, ii) alkali‐metal doping, and iii) an n‐type buffer layer formed on the CGSe film surface is found to a be key to control the energy conversion device parameters, such as the FF and open circuit voltage of solar cells and the onset potential of photoelectrochemical cells, due to the suppression of interface recombination. [ABSTRACT FROM AUTHOR]

The preparation of thin films of nanostructured functional materials is a critical step in a diverse array of applications ranging from photonics to separation science. New thin‐film fabrication methods are sought to harness the emerging potential of self‐assembled nanostructured materials as next‐generation membranes. Here, the authors show that nanometer‐scale control over the thickness of self‐assembled mesophases can be enacted by directional photopolymerization in the presence of highly photo‐attenuating molecular species. Metrology reveals average film growth rates below ten nanometers per second, indicating that high‐resolution fabrication is possible with this approach. The trends in experimental data are reproduced well in numerical simulations of mean‐field frontal photopolymerization modeled in a highly photo‐attenuating and photo‐bleaching medium. These simulation results connect the experimentally observed nanometer‐scale control of film growth to the strong photo‐attenuating nature of the mesophase, which originates from its high‐aromatic‐ring content. Water permeability measurements conducted on the fabricated thin films show the expected linear scaling of permeability with film thickness. Film permeabilities compare favorably with current state‐of‐the‐art nanofiltration and reverse osmosis membranes, suggesting that the current approach may be utilized to prepare new nanoporous membranes for such applications. [ABSTRACT FROM AUTHOR]

Cerium oxide (ceria) is widely used in relation to solid electrolytes in multiple high‐temperature devices, allowing metal components in contact to penetrate into the ceria, especially along the grain boundaries. However, few researchers have concentrated on the migration of metal cations at the operating temperatures (e.g., 600–750 °C) of these devices. Here, the diffusion and solubility of transition metals are investigated through acceptor‐doped ceria grain boundaries as a function of the temperature, pO2, dopant type, and doping concentration. The use of thin‐film samples with high grain boundary density levels and time‐of‐flight secondary ion mass spectrometry with ppb‐level chemical resolution enables an accurate analysis of the concentration profiles of metal species present inside the grain boundaries at such low temperatures. Ni, Fe, and Pt migrate unexpectedly rapidly, and the amounts and types of rare‐earth dopants have a considerable effect on the diffusion of the transition metal. Furthermore, transition metals (Mn, Fe, Co, Ni, and, Cu) are present at the grain boundaries at substantial solubility levels of ≈1022 cm−3, i.e., 1–2 orders of magnitude greater than in the bulk lattice. The observed dynamic behaviors of transition metals present a new perspective on the performance and durability of ceria‐containing applications. [ABSTRACT FROM AUTHOR]