Roland Widmer

Maintaining a stable interface between sulfide solid-state electrolytes and layered oxide cathodes remains a major challenge limiting the performance of all-solid-state batteries. Atomic layer deposition (ALD) of lithium niobate (LNO) on layered oxide cathodes is widely used to stabilize these interfaces, yet the early-stage growth of LNO remains poorly understood and strongly influenced by precursor chemistry. Here, we demonstrate substrate-enhanced ALD growth of LNO on single-crystal LiNi0.82Mn0.07Co0.11O2 (NMC) achieved using commercial lithium–niobium precursor chemistry, enabling complete surface encapsulation with conformal LNO coatings thinner than 8 nm. The resulting ultrathin LNO coatings increase the discharge capacity of Li6PS5Cl-NMC all-solid-state batteries by up to 20% while maintaining good rate capability. The improved electrochemical performance is attributed to the suppressed electrochemical decomposition of the Li6PS5Cl solid-state electrolyte during cycling, as evidenced by X-ray photoelectron spectroscopy, highlighting the importance of controlling the early-stage ALD growth of LNO.

Neat films of organic dyes are an interesting technological platform for solar cells and photodetectors. Recently, the conventional biphasic bulk‐heterojunction paradigm for photoinduced charge separation was challenged by the observation that charge carriers can be photogenerated in single‐component materials. A comprehensive experimental and theoretical study is presented here on neat films of a near‐infrared squaraine dye, recently exploited to build an efficient photodetector relying on a single‐component active material. Experimental data collected on pristine and annealed films lead to the conclusion that field‐assisted photoinduced charge generation mainly occurs in the amorphous phase. This interpretation is fully supported by a theoretical model that, relying on crystallographic data and validated against optical spectra, adopts an essential state description of the squaraine dye and accounts for electrostatic and charge‐transfer intermolecular interactions. In the amorphous domain charge generation is made possible by the large electrostatic disorder induced at molecular sites by the randomly distributed surrounding molecules. Weak coupling between exciton and charge‐transfer states favors the formation of charge‐separated states. The present charge‐generation mechanism is applicable to the squaraine dye family and may also extend to other multibranched donor‐acceptor molecular systems. As such, it provides general guidelines for the rational design of single‐component active materials.

Recent advances in nanomaterials have pushed the boundaries of nanoscale fabrication to the limit of single atoms, particularly in heterogeneous catalysis. Single atom catalysts, comprising minute amounts of transition metals dispersed on inert substrates, have emerged as prominent materials in this domain. However, overcoming the tendency of these single atoms to cluster beyond cryogenic temperatures and precisely arranging them on surfaces with desired local environments pose significant challenges. Employing organic templates for orchestrating and modulating the activity of single atoms holds promise. Here, we introduce an on-surface synthesis of a single atom platform wherein atoms are firmly anchored to specific coordination sites distributed along carbon-based polymers. These platforms exhibit atomic-level structural precision and stability, even at elevated temperatures, offering arrays of undercoordinated metal centers as model active sites for single-atom catalysis. We theoretically reveal the pronounced ability of these architectures to coordinate several gas molecules and experimentally visualize their interaction with CO and CO ₂ . Fine-tuning the structure and properties of the coordination sites offers unparalleled flexibility in tailoring functionalities, thus opening avenues for previously untapped potential in catalytic applications.

The incommensurate spin density wave (SDW) of Chromium represents the classic example of itinerant antiferromagnetism induced by the nesting of the Fermi surface, which is further enriched by the co-presence of a charge density wave (CDW). Here, we explore its electronic band structure using soft-X-ray angle-resolved photoemission spectroscopy (ARPES) for a proper bulk-sensitive investigation. We find that the long-range magnetic order gives rise to a very rich ARPES signal, which can only be interpreted with a proper first-principles description of the SDW and CDW, combined with a band unfolding procedure, reaching a remarkable agreement with experiments. Additional features of the SDW order are obscured by superimposed effects related to the photoemission process, which, unexpectedly, are not predicted by the free-electron model for the final states. We demonstrate that, even for excitation photon energies up to 1 keV, a multiple scattering description of the photoemission final states is required.

Most high-efficiency all-perovskite tandem solar cells use a "superstrate" configuration, integrating a wide-bandgap (WBG) top subcell and a narrow bandgap (NBG) bottom subcell. However, this structure suffers oxidative degradation due to easily air-exposable bottom NBG subcells. A "substrate" structure offers improved stability for tandems by encapsulating the NBG top subcell with the air-stable WBG bottom subcell. However, conventional WBG perovskite solar cells (PSCs) using water-based NiO_x interlayers hinder their fabrication on top of the NBG subcells in an inert atmosphere. To overcome this, we developed a nonaqueous NiO_x nanoparticle dispersion, enabling interlayer fabrication inside a glove box. The blade-coated NiO_x interlayer facilitated the formation of a densely packed 2PACz (2-(9H-carbazol-9-yl)ethyl]phosphonic acid) monolayer hole transporting layer (HTL). The energetically aligned 2PACz molecules reduced minority carrier recombination at the NiO_x/perovskite interface. As a result, the fully scalable 1.77 eV WBG PSCs employing a NiO_x/2PACz hybrid HTL delivered a champion power conversion efficiency of 17.4%.

The emerging field of orbitronics aims to generate and control orbital angular momentum for information processing. Chiral crystals are promising orbitronic materials because they have been predicted to host monopole-like orbital textures, where the orbital angular momentum aligns isotropically with the electron’s crystal momentum. However, such monopoles have not yet been directly observed in chiral crystals. Here, we use circular dichroism in angle-resolved photoelectron spectroscopy to image orbital angular momentum monopoles in the chiral topological semimetals PtGa and PdGa. The spectra show a robust polar texture that rotates around the monopole as a function of photon energy. This is a direct consequence of the underlying magnetic orbital texture and can be understood from the interference of local atomic contributions. Moreover, we also demonstrate that the polarity of the monopoles can be controlled through the structural handedness of the host crystal by imaging orbital angular moment monopoles and antimonopoles in the two enantiomers of PdGa, respectively. Our results highlight the potential of chiral crystals for orbitronic device applications, and our methodology could enable the discovery of even more complicated nodal orbital angular momentum textures that could be exploited for orbitronics.

Atomically precise graphene nanoribbons (GNRs) have a wide range of electronic properties that depend sensitively on their chemical structure. Several types of GNRs have been synthesized on metal surfaces through selective surface-catalyzed reactions. The resulting GNRs are adsorbed on the metal surface, which may lead to hybridization between the GNR orbitals and those of the substrate. This makes investigation of the intrinsic electronic properties of GNRs more difficult and also rules out capacitive gating. Here, we demonstrate the formation of a dielectric gold chloride adlayer that can intercalate underneath GNRs on the Au(111) surface. The intercalated gold chloride adlayer electronically decouples the GNRs from the metal and leads to a substantial hole-doping of the GNRs. Our results introduce an easily accessible tool in the in situ characterization of GNRs grown on Au(111) that allows for exploration of their electronic properties in a heavily hole-doped regime.