Udo Schwingenschlögl

Molecular engineering of evaporated Me‑4PACz and 2PACz SAMs reveals the link between structure to interface quality and tandem performance. Mitigating SAM disorder enables 32.2% efficient fully textured perovskite/silicon tandems.

We conduct a systematic study that couples first-principles lattice dynamics, including three- and four-phonon processes, with parameter-free electronic transport simulations to quantify the thermoelectric response of Ba4Sb2Se and Ba4Sb2Te. Four-phonon processes expand the anharmonic phase space and suppress the lattice thermal conductivity. Directional and doping trends mirror the band structure. Multiple valence and conduction band valleys increase the Seebeck coefficient while keeping the carrier mobility competitive. With three- and four-phonon processes, the peaks of the thermoelectric figure of merit at 700 K are 0.9/1.0 and 0.7/1.0 for Ba4Sb2Se and 0.9/1.2 and 0.9/1.3 for Ba4Sb2Te in the a- and c-directions, respectively, with each pair of values ordered as hole/electron. Altogether, the high thermoelectric figures of merit obtained show that the studied materials offer a promising mid-temperature thermoelectric platform. Explicitly treating four-phonon scattering and selecting the optimal carrier and transport direction are key.

Lead-tin (Pb-Sn) metal halide perovskites (MHPs) with a ∼1.24 eV bandgap are ideal bottom cells in all-perovskite photovoltaic tandems, but Sn2+ instability limits their performance. Traditional additives such as SnF2, metallic Sn, or organic reductants mitigate oxidation but fail to control rapid crystallization, leading to poor film morphology in thick absorbers. Here, phenethylammonium iodide (PEAI), 4-fluorophenethylammonium iodide (4F-PEAI), and 4-fluorophenethylammonium bromide (4F-PEABr) are explored to regulate Pb-Sn perovskite crystallization and enhance stability. These additives improve crystallization, morphology, and device performance. Among them, 4F-PEABr yields the best operational stability under maximum power-point tracking due to fluorine and bromide functionalities that promote slower crystallization and a (111) orientation. The optimized p-i-n perovskite solar cell with an active area of 0.128 cm2 and a device architecture of glass/ITO/PEDOT:PSS/Cs0.05FA0.70MA0.25Pb0.50Sn0.50I3/C60/BCP/Ag achieved a power conversion efficiency of 21.5%, with an open-circuit voltage of 0.83 V, a short-circuit current density of 32.5 mA/cm2, and a fill factor of 80%. This study demonstrates halogen and molecular engineering as effective strategies to achieve efficient and stable Pb-Sn perovskite solar cells for tandem applications.

The advancement of 3D carbon nanostructures for next‐generation desalination membranes is hindered by limited control of the pore size to ensure effective salt rejection. Chemical functionalization and mechanical modification are known approaches to address the problem, while the combined effect of the two approaches remains unexplored. Using classical molecular dynamics simulations, we therefore study their joint potential for carbon honeycomb membranes. We demonstrate for pores with 18–22 Å diameter that 100% salt rejection can be achieved by combined functionalization with ─OH groups and mechanical modification, while maintaining a water permeability two orders of magnitude above that of conventional polyamide membranes. Our simulations enable us to develop a microscopic understanding of the water and salt transport in the carbon honeycomb membranes.

The electronic structure and thermoelectric response of the half‐Heusler compound TaRuAs are studied based on density functional theory, deformation potential theory, and Boltzmann transport theory. The effects of doping are elucidated adopting both the rigid band approximation and supercells that explicitly include the dopant atoms. Our results reveal that TaRuAs has a bandgap of 0.3 eV. The optimal doping concentrations to achieve the highest power factor at 900 K are found to be 2 × 10 ²¹ and 4 × 10 ²¹ cm ⁻³ for hole and electron doping, respectively. Doping at both the Ru and As sites turns out to be an effective method to enhance the thermoelectric figure of merit, with the highest values achieved by TaRu _7/8 Tc _1/8 As (0.4) and TaRuAs _7/8 Ge _1/8 (0.5), respectively.

Noncollinear antiferromagnets can generate a transverse electrical response known as the anomalous Hall effect, even though they possess almost no net magnetization. The microscopic origin of this behaviour, however, has remained unclear because conventional measurement geometries mix different contributions to the measured response. Here, we show that applying magnetic fields in selected in-plane directions allows us to disentangle the mechanisms underlying the Hall effect in a representative noncollinear antiferromagnet. By suppressing any dipole-related signal, we isolate a purely octupole-driven Hall response that exhibits a characteristic three-fold angular symmetry. At low magnetic fields, we further observe an additional Hall-like contribution that arises from the scalar spin chirality associated with noncoplanar spin textures. Combining symmetry analysis, first-principles calculations, and transport measurements, we reveal that octupole order, dipole moments, and chirality coexist and contribute in distinct field regimes. These findings establish a framework for identifying and controlling complex magnetic order parameters for spintronic applications.

Functional-group engineering reveals distinct passivation mechanisms at the perovskite/C ₆₀ interface, enabling the rational design of molecules that balance recombination suppression, device efficiency, and operational stability.

Inverted perovskite solar cells face performance limitations due to non-radiative recombination at the perovskite surfaces in devices, including functional layers. Advanced characterization and density functional theory reveal that phosphonic acids passivate perovskite surface defects, while piperazinium chloride mitigates interface recombination by improving energy level alignment, introducing a field effect, and homogenizing the surface. Together, the quasi-Fermi level splitting of the perovskite is homogeneously increased by ca. 100 mV. This enables two-terminal perovskite-on-silicon tandems to achieve a certified open-circuit voltage of 2 V for a 1 cm² device and high performance in excess of 31%. The scalability of the passivation is furthermore demonstrated with homogeneously passivated devices reaching certified efficiencies of 28.9% for an active area of 60 cm².

The properties of architected materials, such as origami, kirigami, and lattice materials, are determined by the intrinsic properties of the base material and the designed architecture. It is shown that van der Waals interaction between the elements of the architecture is critical for the mechanical properties of nano‐architected triangular graphene. Molecular dynamics simulations demonstrate that interplay between the flexibility and high Young's modulus of graphene, the designed architecture, and the van der Waals interaction between graphene ligaments results in a shape memory effect with a specific energy dissipation of more than 25 times that of the well‐known shape memory alloy NiTi. A shape memory effect with ultrahigh specific energy dissipation is ideal for vibration control and reusable impact absorption devices.