Alexander G. Hufnagel
A5015571612- Nuclear physics research studies
- Iron oxide chemistry and applications
- Perovskite Materials and Applications
- Nuclear Physics and Applications
- Electrocatalysts for Energy Conversion
- Chalcogenide Semiconductor Thin Films
- Advanced Photocatalysis Techniques
- Advanced NMR Techniques and Applications
- Copper-based nanomaterials and applications
- Atomic and Molecular Physics
- Astro and Planetary Science
- Conducting polymers and applications
- Mine drainage and remediation techniques
- Semiconductor materials and devices
- Particle accelerators and beam dynamics
- Fuel Cells and Related Materials
- Astronomical and nuclear sciences
- Metal Extraction and Bioleaching
- Nuclear reactor physics and engineering
- Covalent Organic Framework Applications
- ZnO doping and properties
- Advanced Frequency and Time Standards
- Electrochemical Analysis and Applications
- Advanced Energy Technologies and Civil Engineering Innovations
- Solar-Powered Water Purification Methods
Technical University of Darmstadt
2017-2022
Ludwig-Maximilians-Universität München
2015-2020
Center for NanoScience
2015-2020
Light-driven water electrolysis at a semiconductor surface is promising way to generate hydrogen from sustainable energy sources, but its efficiency limited by the performance of available photoabsorbers. Here we report first time investigation covalent organic frameworks (COFs) as new class photoelectrodes. The presented 2D-COF structure assembled aromatic amine-functionalized tetraphenylethylene and thiophene-based dialdehyde building blocks form conjugated polyimine sheets, which π-stack...
Abstract Covalent organic frameworks (COFs) are an emerging class of highly tuneable crystalline, porous materials. Here we report the first COFs that change their electronic structure reversibly depending on surrounding atmosphere. These can act as solid-state supramolecular solvatochromic sensors show a strong colour when exposed to humidity or solvent vapours, dependent vapour concentration and polarity. The excellent accessibility pores in vertically oriented films results ultrafast...
Abstract Adding cesium (Cs) and rubidium (Rb) cations to FA 0.83 MA 0.17 Pb(I Br ) 3 hybrid lead halide perovskites results in a remarkable improvement solar cell performance, but the origin of enhancement has not been fully understood yet. In this work, time‐of‐flight, time‐resolved microwave conductivity, thermally stimulated current measurements are performed elucidate impact inorganic cation additives on trap landscape charge transport properties within perovskite cells. These...
Abstract A multistep synthesis procedure for the homogeneous coating of a complex porous conductive oxide with small Ir nanoparticles is introduced to obtain highly active electrocatalyst water oxidation. At first, inverse opal macroporous Sb doped SnO 2 (ATO) microparticles defined pore size, composition, and open‐porous morphology are synthesized that reach conductivity ≈3.6 S cm −1 further used as catalyst support. ATO‐supported iridium catalysts controlled amount material prepared by...
The n‐type semiconducting spinel zinc ferrite (ZnFe 2 O 4 ) is used as a photoabsorber material for light‐driven water‐splitting. It prepared the first time by atomic layer deposition. Using resulting well‐defined thin films model system, performance of ZnFe in photoelectrochemical water oxidation characterized. Compared to benchmark α‐Fe 3 (hematite) films, achieve lower photocurrent at reversible potential. However, onset potential 200 mV more cathodic, allowing water‐splitting reaction...
We tune the Fermi level alignment between SnOx electron transport layer (ETL) and Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 highlight that this parameter is interlinked with current–voltage hysteresis in perovskite solar cells (PSCs). Furthermore, thermally stimulated current measurements reveal depth of trap states ETL or at ETL–perovskite interface correlates positions, ultimately linking it to energy difference conduction band minimum. In presence deep states, charge accumulation...
Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure stable and exotic oxygen isotopes at ${\mathrm{R}}^{3}\mathrm{B}/\mathrm{LAND}$ setup with incident beam energies range $300--450\text{ }\mathrm{MeV}/\mathrm{u}$. The isotopic chain offers large variation separation that allows quantitative understanding single-particle strength changing isospin asymmetry. provide complementary approach to intermediate-energy one-nucleon...
Abstract The beneficial effects of Sn(IV) as a dopant in ultrathin hematite (α‐Fe 2 O 3 ) photoanodes for water oxidation are examined. Different Sn concentration profiles prepared by alternating atomic layer deposition Fe and SnO x . Combined data from spectrophotometry intensity‐modulated photocurrent spectroscopy yields the individual process efficiencies light harvesting, charge separation, transfer. best performing Sn‐doped both on surface subsurface region benefit enhanced separation...
Abstract State‐of‐the‐art solar cells based on methylammonium lead iodide (MAPbI 3 ) now reach efficiencies over 20 %. This fast improvement was possible with intensive research in perovskite processing. In particular, chloride‐based precursors are known to have a positive influence the crystallization of perovskite. Here, we used combination in‐situ X‐ray diffraction and charge‐transport measurements understand chloride during planar heterojunction cells. We show that MAPbCl crystallizes...
Abstract A plasma‐enhanced atomic layer deposition (ALD) process is presented, capable of producing thin conformal films nickel(II) oxide (NiO) on various substrates. Nickelocene (NiCp 2 ) used as an inexpensive metal precursor with oxygen plasma the oxidant. The film growth rate saturates both nickel and exposure. An ALD window observed between 225 275 °C. Linear achieved at 250 °C a 0.042 nm per cycle. thickness highly uniform surface roughness below 1 rms for 52 thick Si(100). Substrates...
Background: For many years, quasifree scattering reactions in direct kinematics have been extensively used to study the structure of stable nuclei, demonstrating potential this approach. The RB3 collaboration has performed a pilot experiment inverse for C12 beam. results from that constitute first and complete kinematics. This technique lately extended exotic beams investigate evolution shell structure, which attracted much interest due changes if number protons or neutrons is varied....
Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function binding energy, ultimately when nuclei become unbound, is poorly known. The $^{26}\mathrm{F}$ nucleus, composed deeply bound $\ensuremath{\pi}0{d}_{5/2}$ proton and an unbound $\ensuremath{\nu}0{d}_{3/2}$ neutron on top $^{24}\mathrm{O}$ core, particularly adapted for this purpose. coupling results in...
We present a novel route for the preparation of niobium-doped titanium oxide supported IrO<sub>2</sub> oxygen evolution reaction.
Abstract Hematite-based photoanodes have been intensively studied for photoelectrochemical water oxidation. The n -type dopant Sn has shown to benefit the activity of hematite anodes. We demonstrate in this study that Sn-doped thin films grown by atomic layer deposition can achieve uniform doping across film thickness up at least 32 mol%, far exceeding equilibrium solubility limit less than 1 mol%. On other hand, with introduction doping, crystallite size decreases and many twin boundaries...
The structure of exotic nuclei provides valuable tests for state-of-the-art nuclear theory. In particular electromagnetic transition rates are more sensitive to aspects forces and many-body physics than excitation energies alone. We report the first lifetime measurement excited states in $^{21}$O, finding $\tau_{1/2^+}=420^{+35}_{-32}\text{(stat)}^{+34}_{-12}\text{(sys)}$\,ps. This result together with deduced level scheme branching ratio several $\gamma$-ray decays compared both...
The neutron-unbound isotope $^{13}\mathrm{Be}$ has been studied in several experiments using different reactions, projectile energies, and experimental setups. There is, however, no real consensus the interpretation of data, particular concerning structure low-lying excited states. Gathering new information, which may reveal structure, is a challenge, particularly light its bridging role between $^{12}\mathrm{Be}$, where $N=8$ neutron shell breaks down, Borromean halo nucleus...
We measured 135 cross sections of residual nuclei produced in fragmentation reactions $^{12}\mathrm{C}, ^{14}\mathrm{N}$, and $^{13\ensuremath{-}16,20,22}\mathrm{O}$ projectiles impinging on a carbon target at kinetic energies near $400A$ MeV, most them for the first time, with $\mathrm{R}^{3}\mathrm{B}$/LAND setup GSI facility Darmstadt (Germany). The use this state-of-the-art experimental combination inverse kinematics technique gave full identification atomic mass numbers residues high...
An enhanced low-energy electric dipole (E1) strength is identified for the weakly bound excited states of neutron-rich isotope ^{27}Ne. The Doppler-shift lifetime measurements employing a combination γ-ray tracking array GRETINA, plunger device, and S800 spectrograph determine lower limit 0.030 e^{2} fm^{2} or 0.052 W.u. 1/2^{+}→3/2^{-} E1 transition in ^{27}Ne, representing one strongest strengths observed among discrete this mass region. This value at least 30 times larger than that...
In article number 1703057, Andreas Baumann, Tom J. Savenije, Michiel L. Petrus, Pablo Docampo and co-workers demonstrate that the incorporation of Cs+ cations into lead halide perovskites reduces trapping photogenerated charge carriers in deep trap states. This can be related to an increase open-circuit voltage perovskite solar cells. Cover Image by Christoph Hohmann, Nanosystems Initiative Munich (NIM).
Understanding the Role of Cesium and Rubidium Additives in Perovskite Solar Cells: Trap States Charge Carrier MobilityYinghong Hu a, Eline M. Hutter b, Philipp Rieder c, Irene Grill Jonas Hanisch d, Meltem F. Aygüler Alexander G. Hufnagel Matthias Handloser e, Thomas Bein Achim Hartschuh Kristofer Tvingstedt Vladimir Dyakonov Andreas Baumann f, Tom J. Savenije Michiel L. Petrus Pablo Docampo ga University Munich (LMU), Department Chemistry Center for Nanoscience (CeNS), 81377 Múnich,...
Photoelectrical water oxidation by photoanodes comprised of ultrathin hematite films is investigated Christina Scheu, Rossitza Pentcheva, and co-workers in article number 1804472. It determined that on-surface tin doping prevents hole-trapping lowers the overpotential. Sub-surface doping, provided bulk remains undoped, introduces a band gradient, thereby enhancing charge separation efficiency. The results will be useful developing high-performance splitting systems.
Photoelectrolysis of water is a promising technology to generate hydrogen as renewable fuel. In the article on page 4435, T. Bein and co-workers examine kinetics photoelectrochemical water-splitting ultrathin zinc ferrite films. Its intrinsically slow electron/hole recombination, resulting in high charge-transfer efficiency, renders an attractive photoanode material, whose performance further increased by nanomorphology optimization. Cover image designed Christoph Hohmann, Nanosystems...
In article number 1906670, Daniel Böhm, Dina Fattakhova-Rohlfing, and co-workers present a novel scalable approach for the design of dimensionally stable iridium-based oxygen evolution reaction (OER) catalyst architecture with very low iridium volumetric loading density but high OER activity, achieved by conformal deposition ultrasmall IrO2 nanoparticles on porous microparticles serving as support. Cover image designed Christoph Hohmann, Munich Center Quantum Science Technology.