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Thin-film transistors made from indium gallium zinc oxide (IGZO) are driving the next evolution in active-matrix flat panel displays. Hideo Hosono recounts how demand for a high-performance alternative to amorphous silicon transistors led to their development.

Transparent conducting oxides are wide bandgap conductors that have found a range of applications in optoelectronic devices. In this study, Hosono and colleagues fabricate the first transparent conducting oxide based on germanium.

Water is composed of the electrochemically active species, H⁺ and OH⁻, but has not been used as an active electronic material. In this study, a field-effect transistor is developed that uses water-infiltrated nanoporous glass as the gate insulator; this new application of water may be useful in electronics and energy storage.

Developing Ru-intermetallic catalysts for mild ammonia synthesis faces structural complexity. Here, machine learning identified Sc_1/8Nd_7/8Ru₂, optimizing Ru–N bonding and orbital hybridization, enhancing catalytic activity under mild conditions.

The iron pnictides are a class of superconductors that have received widespread interest in recent years. By doping the prototypical material LaFeAsO with hydrogen, this study reveals the existence of a second superconducting dome at higher doping ranges, which arises due to orbital fluctuations.

The superconducting phase of alkali-metal-intercalated iron-selenide superconductors is difficult to study because of a tendency to separate into multiple phases. Guo et al. report the identification of three new iron-selenide superconducting phases, one of which shows the ThCr₂Si₂-type structure.

High critical temperature superconductors could be used to produce ideal electric power lines, but the misalignment of crystalline grain boundaries reduces current density. Here, pnictide superconductors are found to be more tolerant to misaligned grain boundaries than cuprates.

Ammonia synthesis is an energy-intensive process due to the high activation barrier for N₂ dissociation. Here, Hosono and co-workers show that the intermetallic compound LaCoSi can lower the energy requirement for N₂ activation and shift the rate-determining step of the process to NH _x formation under mild conditions.

The authors report very high in-field critical current densities in Fe-based superconductors. They achieve this through doping to increase the carrier density and adding defects to pin vortices.

Transparent, metallic conducting thin films are key for applications such as flatpanel displays and solar cells, and heavily electron-doped ionic oxide materials have been intensively studied for this purpose. A class of conductors that are transparent in the near-infrared region has now been developed using a topological insulator.

N₂ reduction to ammonia typically requires transition metal catalysts, proceeding via a strong metal–nitrogen interaction. Now a Ba–Si orthosilicate oxynitride–hydride has been shown to function as a transition-metal-free catalyst for ammonia synthesis through an anion-vacancy-mediated mechanism, where electrons at the vacancy sites facilitate N₂ activation.

Single-atom catalysts commonly present a random distribution of the active metal centres. Now a series of Mg-rich intermetallic compounds is introduced to enable ordered dispersed active metals. Furthermore, a cascade process is demonstrated on Mg₂₉Pd_1.3Rh_2.7, where Pd sites catalyse the semihydrogenation of phenylacetylene with subsequent hydroformylation on Rh sites.

The application of pressure can raise the superconducting transition temperature of oxypnictide (a pnicogen being a group V element) substantially, to a maximum value of about 43 K. This is the highest transition temperature yet reported for a non-copper-based material, but this record is unlikely to last for long: the material system offers considerable flexibility for chemical modification, and we can reasonably anticipate that this record will soon be superseded.

The presence of electrically active defects on the surface of the support has been shown to be effective for N₂ activation. Here the authors discover that electron-rich polyanionic NH²⁻ defect allows for efficient ammonia synthesis via multiple reaction pathway by incorporating various affordable transition metals.

Effective activation and spitting of carbon dioxide are important steps in its conversion to valuable chemicals. Here the authors report an inorganic electride material with a high concentration of near-surface electrons that is capable of adsorbing and decomposing carbon dioxide.

Development of catalysts that enhance dissociation of the nitrogen–nitrogen triple bond will reduce costs of ammonia production. Here, the authors study ammonia synthesis over a ruthenium loaded electride catalyst and show that the rate-determining step is shifted to nitrogen–hydrogen bond formation.

By understanding the origins of instability in high-mobility amorphous oxide transistors, ultrastable thin-film transistors with mobilities of 70 cm² (V s)^–1 can be fabricated.

The ionic crystal Ca₂N is shown to be an electride in terms of [Ca₂N]⁺·e⁻, with diffusive two-dimensional transport in dense electron layers.

Entropic elasticity, typical of rubbers and known to also occur in organic polymers with certain network structures, is now demonstrated for phosphate-glass fibres with highly anisotropic structures.

Two-dimensional materials are promising for electrochemical storage and conversion, but are somewhat limited in composition. Here the authors use a computational strategy to predict the existence of a layered boride material, which they synthesize and demonstrate prospective for use as an anode material.

Stabilize the active metal single atoms under harsh conditions is critical for the development of single atom catalysts. Here the authors report a nanoporous crystal, 12CaO·7Al₂O₃, that can firmly stabilize Pt single atoms in its surface cavities for efficient catalytic hydrogenation of nitroarenes.

In Suzuki coupling reactions, excellent catalytic performance require negatively charged Pd species and the avoidance of metal leaching or clustering. Here the authors implanted Pd sites into an intermetallic electride, Y₃Pd₂, which serves as an efficient and stable catalyst for Suzuki coupling reactions.

Ammonia is synthesized using a dual-site approach, whereby nitrogen vacancies on LaN activate N₂, which then reacts with hydrogen atoms produced over the Ni metal to give ammonia.

Hydride ions are promising for energy storage since they are abundant, lightweight, and highly mobile, but ionic conductivity should be improved. Here the authors achieve fast hydride ion conductivity in a mixed-anion compound by tuning oxygen content.

Ammonia synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic ammonia synthesis at lower temperatures.

Methods that fix atmospheric nitrogen to ammonia under mild conditions could offer a more environmentally benign alternative to the Haber–Bosch process. Now, a Ru-loaded electride, [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄, is reported that acts as an efficient electron donor and reversible hydrogen store, and is demonstrated to function as an efficient catalyst for ammonia synthesis.

The oxidation state of hydride ions in oxide hosts is a matter of debate. Here, the authors address this question with a range of techniques and suggest that the electron density near an incorporated hydride ion is less than that at the hydrogen in a hydroxide ion, contrary to formal valence arguments.

Nitride semiconductors are attractive for various applications. Here a computational screening study identifies a number of possible ternary nitrides as promising candidates, including a phase that the authors synthesize for the first time via a high-pressure route.

Light-emitting diodes are attractive sources of light used in an increasing range of applications. This study presents a novel europium-based phosphor that gives rise to a substantial reduction in the glare that often makes LEDs uncomfortable to the human eye.

Distinct electronic and optical properties emerge from quantum confinement in low-dimensional materials. Here, combining optical characterization and ab initio calculations, the authors report an unconventional excitonic state and bound phonon sideband in layered silicon diphosphide.

Ferromagnetic quasi-atomic behavior of interstitial anionic electrons (IAEs) in practical electrides is yet to be discovered experimentally. Here, the authors reveal that IAEs in two-dimensional electride [Gd₂C]²⁺⋅2e^- behave as magnetic elements with their own magnetic moment.

Crystalline Ga₂O₃ is an ultra-wide bandgap oxide semiconductor, but electron conduction in amorphous Ga₂O_x has never been attained to date. Here we succeeded in converting amorphous Ga₂O_x to a semiconductor with the bandgap of ~4.12 eV and the electron mobility ~8 cm² V⁻¹ s⁻¹. The key is to suppress charge compensation defects by increasing the film density and suppress formation of oxygen-poor and oxygen-excess defects. It produces thin-film transistors and Schottky diodes with high on currents and on/off ratios.

Oxynitride-supported Ni catalysts exhibit much higher activity than oxide-supported Ni catalysts for ammonia decomposition reaction. Ammonia is activated at nitrogen vacancy sites on the surface of oxynitride in close vicinity to the supported Ni nanoparticles rather than on the Ni surface, and therefore the catalytic performance is dominated by ease of nitrogen vacancy formation on the catalyst surface.