A5030361692- Conducting polymers and applications
- Organic Electronics and Photovoltaics
- Organic Light-Emitting Diodes Research
- Thin-Film Transistor Technologies
- Electron Spin Resonance Studies
- Silicon and Solar Cell Technologies
- Molecular Junctions and Nanostructures
- Silicon Nanostructures and Photoluminescence
- Perovskite Materials and Applications
- Lanthanide and Transition Metal Complexes
- Quantum and electron transport phenomena
- Semiconductor materials and interfaces
- Photochemistry and Electron Transfer Studies
- Graphene research and applications
- Fullerene Chemistry and Applications
- Semiconductor materials and devices
- Fuel Cells and Related Materials
- Atomic and Subatomic Physics Research
- Organic and Molecular Conductors Research
- Magnetism in coordination complexes
- Electrocatalysts for Energy Conversion
- Diamond and Carbon-based Materials Research
- Advanced NMR Techniques and Applications
- Advanced battery technologies research
- Solid-state spectroscopy and crystallography
Freie Universität Berlin
2016-2025
Radboud University Nijmegen
2022
Helmholtz-Zentrum Berlin für Materialien und Energie
2008-2016
Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute
2006-2008
Today, most metal and nitrogen doped carbon catalysts for ORR reveal a heterogeneous composition. This can be reasoned by nonoptimized precursor composition various steps in the preparation process to get required active material. The significant presence of inorganic species interferes with assignment descriptors related activity stability. In this work we present simple feasible way reduce contribution some cases even down zero. Such desired homogeneous MeN4 (Me = metal) sites that is...
New polymers with high electron mobilities have spurred research in organic solar cells using polymeric rather than fullerene acceptors due to their potential of increased diversity, stability, and scalability. However, all‐polymer struggled keep up the steadily increasing power conversion efficiency polymer:fullerene cells. The lack knowledge about dominant recombination process as well missing concluding picture on role semi‐crystalline microstructure conjugated free charge carrier...
State‐of‐the‐art p‐type doping of organic semiconductors is usually achieved by employing strong π‐electron acceptors, a prominent example being tetrafluorotetracyanoquinodimethane (F 4 TCNQ). Here, the semiconducting model polymer poly(3‐hexylthiophene), P3HT, using Lewis acid tris(pentafluorophenyl)borane (BCF) as dopant, investigated admittance, conductivity, and electron paramagnetic resonance measurements. The electrical characteristics BCF‐ F TCNQ‐doped P3HT layers are shown to be very...
Using time-resolved electron paramagnetic resonance (EPR) spectroscopy in conjunction with optical excitation we study charge separation conjugated polymers blended [6,6]-phenyl C61-butyric acid methyl ester (PCBM). A direct comparison between samples comprising poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (C-PCPDTBT) and their analogues containing...
The mechanism and the nature of species formed by molecular doping model polymer poly(3-hexylthiophene) (P3HT) in its regioregular (rre-) regiorandom (rra-) forms solution are investigated for three different dopants: prototypical π-electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), strong Lewis acid tris(pentafluorophenyl)borane (BCF), strongly oxidizing complex molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-CO2Me)3). In a...
Singlet fission (SF), an exciton-doubling process observed in certain molecular semiconductors where two triplet excitons are generated from one singlet exciton, requires correctly tuned intermolecular coupling to allow separation of the triplets different units. We explore this using DNA-encoded assembly SF-capable pentacenes into discrete π-stacked constructs defined size and geometry. Precise structural control is achieved via a combination DNA duplex formation between complementary...
We report the observation of a spin-dependent dark transport current, exhibiting spin coherence at room temperature, in $\ensuremath{\pi}$-conjugated polymer-fullerene blend using pulsed electrically detected magnetic resonance. The resonance $g=2.0028(3)$ is due to polarons polymer, and exhibits locking high microwave fields. presence an excess fullerene, operating voltage (1 V) used, suppresses negative polaron formation polymer. It concluded that positive bipolarons.
We report transient electron paramagnetic resonance (trEPR) measurements with submicrosecond time resolution performed on a polymer:fullerene blend consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl ${\mathrm{C}}_{61}$-butyric acid methyl ester (PCBM) at low temperatures. The trEPR spectrum immediately following photoexcitation reveals signatures spin-correlated polaron pairs. pair partners (positive polarons in P3HT negative PCBM) can be identified by their characteristic $g$...
Significance Pairs of spins in molecular materials have attracted significant interest as intermediates photovoltaic devices and light-emitting diodes. However, isolating the local spin electronic environments such has proved challenging due to complex structures which they reside. Here we show how exchange coupling can be used select characterize multiple coexisting pairs, enabling joint measurement their interactions optical profiles. We apply this spin-1 pairs formed by photon absorption...
Abstract Molecular doping allows enhancement and precise control of electrical properties organic semiconductors, is thus central technological relevance for (opto‐) electronics. Beyond single‐component molecular electron acceptors donors, salts have recently emerged as a promising class dopants. However, the pertinent fundamental understanding mechanisms capabilities limited. Here, unique salt consisting borinium cation (Mes 2 B + ; Mes: mesitylene) tetrakis(penta‐fluorophenyl)borate anion...
Abstract We report a fully efficient singlet exciton fission material with high ambient chemical stability. 10,21- Bis(triisopropylsilylethynyl)tetrabenzo[a,c,l,n]pentacene (TTBP) combines an acene core triphenylene wings that protect the formal pentacene from degradation. The electronic energy levels position to be endothermic, similar tetracene despite triphenylenes. TTBP exhibits rapid early time quantitative yield of triplet pairs within 100 ps followed by thermally activated separation...
A versatile on-substrate electrode setup was developed and used to perform quantitative in operando EPR as well low-temperature pulse experiments on electrochemical cells containing a redox conductive polymer energy-storage material.
We investigate the delocalization of holes in semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring hyperfine coupling between photogenerated polarons and bound nuclear spins using electron double resonance spectroscopy. An extrapolation corresponding oligomer spectra reveals that charges tend to delocalize over 4.0-4.8 nm with strongly dependent on molecular order crystallinity PBTTT thin films. Density functional theory...
Frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) based on coherent synchrotron radiation (CSR) is presented as a novel tool to ascertain very large zero field splittings in transition metal ion complexes. A description of the FD-FT THz-EPR at BESSY II storage ring providing CSR frequency range from 5 cm−1 up 40 external magnetic fields −10 T +10 given together with first measurements single molecule magnet Mn12Ac where we studied ΔMS = ±1 spin energies...
Combining orientation dependent electrically detected magnetic resonance and $g$ tensor calculations based on density functional theory we assign microscopic structures to paramagnetic states involved in spin-dependent recombination at the interface of hydrogenated amorphous silicon crystalline ($a\mathrm{\text{\ensuremath{-}}}\mathrm{Si}:\mathrm{H}/c\mathrm{\text{\ensuremath{-}}}\mathrm{Si}$) heterojunction solar cells. We find that (i) exhibits roughness, (ii) electronic structure defects...
The modern picture of negative charge carriers on conjugated polymers invokes the formation a singly occupied (spin-up/spin-down) level within polymer gap and corresponding unoccupied above conduction band edge. energy splitting between these sublevels is related to on-site Coulomb interactions electrons, commonly termed Hubbard U. However, spectral evidence for both experimental access U value still missing. Here, we provide by n-doping P(NDI2OD-T2) with [RhCp*Cp]2, [N-DMBI]2, cesium....
Salen-type complexes with transition metals and corresponding polymers attract great scientific interest due to their outstanding electrochemical properties catalytic potential. Cobalt of this kind are known as catalysts for a large variety redox reactions, including oxygen reduction. Herein, we report the preparation modified cobalt complex, by TEMPO pendants linked core flexible butylenedioxy linkers. The resulting product was characterized electrospray–high-resolution mass spectrometry...
Conductive polymers with TEMPO pendants are considered as a promising class of energy storage materials. However, the rational design such materials demands for minimization molar mass unit. The utilization PROXYL stable radical instead may decrease weight monomeric unit and, thus, improve capacity Herein, we report NiSalen complex 3-carboxy-PROXYL pendants, designed to complex. resulting product was characterized by 1H NMR, electrospray high-resolution spectrometry and EPR.
Abstract Nanoribbons, nanometre-wide strips of a two-dimensional material, are unique system in condensed matter. They combine the exotic electronic structures low-dimensional materials with an enhanced number exposed edges, where phenomena including ultralong spin coherence times 1,2 , quantum confinement 3 and topologically protected states 4,5 can emerge. An exciting prospect for this material concept is potential both tunable semiconducting structure magnetism along nanoribbon edge, key...
In thin film solar cells based on non-crystalline silicon or organic semiconductors structural disorder leads to localized states that induce device limiting charge recombination and trapping. Both processes frequently involve paramagnetic become spin-dependent. the present perspectives article we report advanced pulsed electrically detected magnetic resonance (pEDMR) experiments for study of spin dependent transport in fully processed cells. We reflect recent advances pEDMR spectroscopy...
An experimental technique allows researchers to probe and utilize the properties of enigmatic multiexciton quintet states (with a spin 2), state that is otherwise difficult study but has potential applications in spin-based technologies.
Abstract Redox‐active nitroxyl‐containing polymers are promising candidates as possible replacements for inorganic based energy‐storage materials, due to their high energy density and fast redox kinetics. One challenge towards the implementation of such a system is insufficient electrical conductivity, impeding charge collection even with highly conductive additives. Herein, first polymeric bis(salicylideniminato) nickel (NiSalen) backbone an active charge‐collecting wire reported. NiSalen...
Natural photosystems use protein scaffolds to control intermolecular interactions that enable exciton flow, charge generation, and long-range separation. In contrast, there is limited structural in current organic electronic devices such as OLEDs solar cells. We report here the DNA-encoded assembly of π-conjugated perylene diimides (PDIs) with deterministic over number electronically coupled molecules. The PDIs are integrated within DNA chains using phosphoramidite coupling chemistry,...