PD Dr. Sylke Blumstengel
Profil
Forschungsthemen3
SFB 951/1: HIOS - Electronic coupling in inorganic/organic semiconductor hybrid structures for opto-electronic function (TP B 3)
Quelle ↗409-01-A · Algorithmik und KomplexitätFörderer: DFG Sonderforschungsbereich Zeitraum: 07/2011 - 06/2015 Projektleitung: PD Dr. Sylke Blumstengel
SFB 951/2: HIOS – Elektronische Kopplung in anorganisch/organischen Halbleiterhybridstrukturen für opto-elektronische Funktionen (TP B03)
Quelle ↗Förderer: DFG Sonderforschungsbereich Zeitraum: 07/2015 - 06/2019 Projektleitung: PD Dr. Sylke Blumstengel
SFB 951/3: Elektronische Kopplung in anorganisch/organischen Halbleiterhybridstrukturen für opto-elektronische Funktionen (TP B03)
Quelle ↗Förderer: DFG Sonderforschungsbereich Zeitraum: 07/2019 - 06/2023 Projektleitung: PD Dr. Sylke Blumstengel
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Stand: 26.4.2026, 19:48:44 (Top-K=20, Min-Cosine=0.4)
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Publikationen25
Top 25 nach Zitationen — Quelle: OpenAlex (BAAI/bge-m3 embedded für Matching).
Physical review. B, Condensed matter · 348 Zitationen · DOI
The effects of weak magnetic fields on the photoconductivity of poly(p-phenylene vinylene) (PPV) and two derivatives, poly(1,4-phenylene-1,2-dimethoxyphenyl vinylene) (DMOP-PPV) and poly(2-phenyl-1,4-phenylene vinylene) (PPPV), were observed within the temperature range 130--350 K. These effects are attributed to the formation of interchain pairs involving a negative polaron and a positive polaron. A polaron pair is formed as a result of interchain electron transfer from a molecular exciton. The lifetime of a pair is estimated to be within the range of ${10}^{\mathrm{\ensuremath{-}}8--}$${10}^{\mathrm{\ensuremath{-}}9}$ s. Thermal dissociation of a polaron pair produces free charge carriers, and recombination of the pair regenerates a singlet or triplet exciton on a single conjugated segment of a chain.
Applied Physics Letters · 158 Zitationen · DOI
Single-phase ZnCdO alloys with a band gap extending from the violet to yellow spectral range are fabricated by molecular beam epitaxy using extremely low growth temperatures in conjunction with O-rich growth conditions. The Cd concentration can be systematically adjusted via the Cd∕Zn beam pressure ratio. Despite growth temperatures as low as 150°C, layer-by-layer growth is accomplished allowing for the preparation of ZnCdO∕ZnO quantum well structures. Both epilayers and quantum wells exhibit strong band-gap-related emission at room temperature in the whole composition range.
Applied Physics Letters · 131 Zitationen · DOI
We report on a specific growth procedure combining low-temperature growth of ZnMgO and postgrowth annealing at intermediate temperatures. Despite the large lattice misfit induced by the sapphire substrate, layer-by-layer growth is accomplished up to the phase-separation limit found at a c-lattice constant of 0.5136nm and Mg mole fraction of 0.40. The procedure allows us to grow quantum wells with atomically smooth interfaces in a wide range of structural designs exhibiting prominent emission features up to room temperature.
Physical Review B · 121 Zitationen · DOI
We show that the work function (\ensuremath{\Phi}) of ZnO can be increased by up to 2.8 eV by depositing the molecular electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). On metals, already much smaller \ensuremath{\Phi} increases involve significant charge transfer to F4TCNQ. No indication of negatively charged F4TCNQ on ZnO is found by photoemission spectroscopy. This fundamental difference is explained by a simple electrostatic model that identifies the bulk doping and band bending in ZnO as key parameters. Varying \ensuremath{\Phi} of the inorganic semiconductor enables tuning the energy-level alignment at ZnO/organic semiconductor interfaces.
Converting Wannier into Frenkel Excitons in an Inorganic/Organic Hybrid Semiconductor Nanostructure
2006Physical Review Letters · 120 Zitationen · DOI
Electronic coupling between Wannier and Frenkel excitons in an inorganic/organic semiconductor hybrid structure is experimentally observed. Time-resolved photoluminescence and excitation spectroscopy directly demonstrate that electronic excitation energy can be transferred with an efficiency of up to 50% from an inorganic ZnO quantum well to an organic [2,2-p-phenylenebis-(5-phenyloxazol), alpha-sexithiophene] overlayer. The coupling is mediated via dipole-dipole-interaction analog to the Förster transfer in donor-acceptor systems.
Nature Communications · 112 Zitationen · DOI
The fundamental limits of inorganic semiconductors for light emitting applications, such as holographic displays, biomedical imaging and ultrafast data processing and communication, might be overcome by hybridization with their organic counterparts, which feature enhanced frequency response and colour range. Innovative hybrid inorganic/organic structures exploit efficient electrical injection and high excitation density of inorganic semiconductors and subsequent energy transfer to the organic semiconductor, provided that the radiative emission yield is high. An inherent obstacle to that end is the unfavourable energy level offset at hybrid inorganic/organic structures, which rather facilitates charge transfer that quenches light emission. Here, we introduce a technologically relevant method to optimize the hybrid structure's energy levels, here comprising ZnO and a tailored ladder-type oligophenylene. The ZnO work function is substantially lowered with an organometallic donor monolayer, aligning the frontier levels of the inorganic and organic semiconductors. This increases the hybrid structure's radiative emission yield sevenfold, validating the relevance of our approach.
Physical Review Letters · 77 Zitationen · DOI
We discuss density functional theory calculations of hybrid inorganic-organic systems that explicitly include the global effects of doping (i.e., position of the Fermi level) and the formation of a space-charge layer. For the example of tetrafluoro-tetracyanoquinodimethane on the ZnO(0001[over ¯]) surface we show that the adsorption energy and electron transfer depend strongly on the ZnO doping. The associated work function changes are large, for which the formation of space-charge layers is the main driving force. The prominent doping effects are expected to be quite general for charge-transfer interfaces in hybrid inorganic-organic systems and important for device design.
Journal of Materials Chemistry · 54 Zitationen · DOI
A novel synthetic route to even-numbered ladder-type oligo(p-phenylene)s (LOPPs) carrying no solubilizing groups to facilitate vacuum-processing is presented. The influence of increasing bridging adjacent phenylene units on the optical and electrochemical properties is discussed in the series of p-sexiphenyl 6P, terfluorene 3F, and ladder-type sexiphenyl L6P. The influence of the extension of the π-system is taken into consideration as well. Furthermore it is shown that highly ordered thin films of L6P on alumina surfaces can be prepared by organic molecular beam deposition (OMBD).
Physical review. B./Physical review. B · 51 Zitationen · DOI
We demonstrate the capability of two molecular organic acceptors [1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile and 2,2\ensuremath{'}-(perfluoronaphthalene-2,6-diylidene)dimalononitrile] to tune the work function (\ensuremath{\Phi}) of intrinsically doped GaN(0001) and for comparison of intrinsically doped ZnO(0001). With ultraviolet photoelectron spectroscopy we determine the accessible \ensuremath{\Phi} range as 4.2--6.0 eV for GaN and 3.9--6.3 eV for ZnO. The contribution to the \ensuremath{\Phi} change (\ensuremath{\Delta}\ensuremath{\Phi}) of acceptor-induced surface band bending within GaN was significantly smaller than in ZnO (0.35 versus 1 eV), which we attribute to surface gap states. We introduce a model that takes these surface states into account and thus allows quantifying the impact of the semiconductor bulk doping level and surface state density on \ensuremath{\Delta}\ensuremath{\Phi}. The lower the doping level is, the lower the surface state density needs to be to reduce the band bending contribution to \ensuremath{\Delta}\ensuremath{\Phi}. This limits the maximum value of \ensuremath{\Phi} tuning for GaN with molecular acceptors, whereas, on the other hand, it renders the method robust against surface structural disorder.
Applied Physics Letters · 46 Zitationen · DOI
Optical gain and lasing properties of ZnO∕ZnMgO multiple quantum wells with and without separate optical confinement are investigated in the temperature range from 5to290K. The data signify that localized states are crucially involved in the laser action up to room temperature. The lasing threshold increases by about one order of magnitude and reaches 140kW∕cm2 at 290K. The room temperature material gain is in the 103cm−1 range.
Applied Physics Letters · 44 Zitationen · DOI
We report on a dramatic improvement of the crystalline quality of ZnMgO and ZnCdO epilayers using Bridgman-grown ZnO substrates. ZnMgO alloys grow pseudomorphically over several 100nm and the (0002) ω-rocking curve width is as low as 19arcsec. Strain inhomogeneities in low-temperature grown ZnCdO are significantly reduced and the rocking width is lowered down to 45arcsec. Despite the high crystalline perfection, the optical properties of the films are mainly determined by their ternary character.
New Journal of Physics · 43 Zitationen · DOI
The epitaxial growth of small conjugated molecules on ZnO-based surfaces is studied. A weak substrate interaction allows for the preparation of organic layers with well-defined morphology and electronically intact interfaces without the need for extra passivation. Nonradiative energy transfer from inorganic quantum wells to various molecules is identified by optical spectroscopy. The strength of the dipole–dipole mediated coupling between Wannier and Frenkel excitons is as large as 2 meV. In hybrid structures with type-II energy level alignment, charge separation occurs at the organic/inorganic interface as well. These findings render organic/ZnO hybrid structures interesting for light-emitting as well as photovoltaic applications benefiting from favorable properties of both material classes.
Applied Physics Letters · 43 Zitationen · DOI
We report on laser action of ZnCdO∕ZnO quantum well structures up to room temperature under optical pumping. Prerequisite is a novel annealing step increasing the radiative efficiency of the low-temperature grown structures by more than one order of magnitude. The carrier states involved are localized making the lasing properties temperature robust. The longest wavelength reached so far is 490nm.
The Journal of Physical Chemistry C · 42 Zitationen · DOI
Monolayer (ML) transition-metal dichalcogenides (TMDCs) are an attracting new class of two-dimensional direct band gap semiconducting materials for optoelectronic device applications. The combination of TMDCs with organic semiconductors holds the promise to further improve device properties with added functionality. Here, we demonstrate that excited-state charge transfer from a thin organic absorber layer, i.e., metal-free phthalocyanine (H2Pc), enhances the photoresponse of ML MoS2 dramatically at the same time also significantly extending it to spectral regions where the TMDC is transparent. The fundamental processes enabling this boost in photodetector performance are unraveled by a combination of photoemission (PES), photoluminescence (PL), and photocurrent action spectroscopy. Direct and inverse PES reveal a type II energy level alignment at the MoS2/H2Pc interface with a large energy offset of 1 eV, which is sufficient to drive the excited-state charge transfer. Time-resolved PL measurements evidence highly efficient dissociation of excitons generated in H2Pc when they are in contact with MoS2. Exciton dissociation results in the formation of a charge-separated state at the hybrid interface with an energy gap of ca. 1.2 eV, in accordance with PES. This state then dissociates into free carriers and markedly contributes to the current in the photodetector, as demonstrated by photocurrent action spectroscopy. This reveals that the photoconductivity within the MoS2 ML is generated by light directly absorbed in the TMDC and, notably, with comparable efficiency by the absorption by H2Pc. The present demonstration of a highly efficient carrier generation in TMDC/organic hybrid structures paves the way for future nanoscale photodetectors with very wide spectral sensitivity.
Advanced Materials · 42 Zitationen · DOI
Polarized light over a large spectral region is provided by the novel procedure described in this work. The active material of these light-emitting diodes (LEDs) is formed by two polymer layers that are oriented perpendicularly to each other. The orientation is obtained using the rubbing technique combined with thermal annealing. The Figure represents the electroluminescence (EL) emission from the two-layer LED and its structure (see also inside front cover).
Morphology-, synthesis- and doping-independent tuning of ZnO work function using phenylphosphonates
2014Physical Chemistry Chemical Physics · 41 Zitationen · DOI
The work function (WF) of ZnO is modified by two types of dipole-bearing phenylphosphonate layers, yielding a maximum WF span of 1.2 eV. H3CO-phenyl phosphonate, with a positive dipole (positive pole pointing outwards from the surface), lowers the WF by ∼350 meV. NC-phenyl phosphonate, with a negative dipole, increases the WF by ∼750 meV. The WF shift is found to be independent of the type of ZnO surface. XPS data show strong molecular dipoles between the phenyl and the functionalizing (CN and OMe) tail groups, while an opposite dipole evolves in each molecular layer between the surface and the phenyl rings. The molecular modification is found to be invariant to supra-bandgap illumination, which indicates that the substrate's space charge-induced built-in potential is unlikely to be the reason for the WF difference. ZnO, grown by several different methods, with different degrees of crystalline perfection and various morphologies and crystallite dimensions, could all be modified to the same extent. Furthermore, a mixture of opposite dipoles allows gradual and continuous tuning of the WF, varying linearly with the partial concentration of the CN-terminated phosphonate in the solution. Exposure to the phosphonic acids during the molecular layer deposition process erodes a few atomic layers of the ZnO. The general validity of the treatment and the fine-tuning of the WF of treated interfaces are of interest for solar cells and LED applications.
Applied Physics Letters · 38 Zitationen · DOI
Optical and electroluminescent properties of a new poly(p-phenylene)-type polymer, poly(benzoyl-1, 4-phenylene) (PBP) were studied. PBP is soluble in common organic solvents, has high thermal stability and shows bright blue photoluminescence. Light-emitting diodes fabricated with PBP as the active layer emit blue electroluminescence with a peak wavelength at 446 nm and a brightness of about 100 cd/m2.
Applied Physics Letters · 33 Zitationen · DOI
Interface formation between the organic semiconductor α-sexithiophene (6T) and polar as well as nonpolar ZnO surfaces is investigated. The growth mode of the organic layer is strongly influenced by the orientation of the ZnO surface. No indication for chemisorption of 6T on ZnO is found by photoelectron spectroscopy. The energy level alignment at the 6T/ZnO interface is of type-II facilitating electron transfer from the organic to the inorganic part and hole transfer in the other direction, rendering this heterostructure interesting for photovoltaic applications.
Physical Review B · 31 Zitationen · DOI
Electronic coupling in a hybrid structure made of ZnMgO and a spirobifluorene derivative (SP6) is investigated in the situation where the energy level alignment at the organic/inorganic interface revealed by photoelectron spectroscopy is of type II. Charge separation caused by electron transfer from the SP6 lowest unoccupied molecular orbital to the conduction band of the semiconductor is observed. By collecting the photogenerated carriers in a ZnO quantum well, very efficient exciton transfer from the inorganic to the organic part occurs as well.
The Journal of Chemical Physics · 31 Zitationen · DOI
In order to obtain efficient organic light-emitting diodes (OLED) it is necessary to funnel both singlet and triplet excitons generated by electroexcitation to the emitting dye molecule. Energy transfer plays thereby a decisive role. We have studied mechanisms and kinetics of the energy transfer process involving singlet and triplet excitations in a donor–acceptor system suitable for use as active layer in OLEDs. Fluorescent and phosphorescent tris(phenylquinoxaline) served as donor and a red emitting platinum porphyrin as acceptor molecule. The results of our investigations show that efficient energy transfer from the singlet and triplet excited state of the donor to the acceptor molecules takes place by combined long-range dipole–dipole interaction and diffusion. Due to the very different oscillator strengths of radiative transitions from the singlet and triplet excited state to the singlet ground state the rate of energy transfer of triplet excitons is several orders of magnitude slower than that of singlet excitons. Since, however, the lifetime of both states differ by the same order of magnitude the transfer efficiency is comparable.
Physical Review Letters · 30 Zitationen · DOI
We study the physisorption of organic oligomers on the strongly ionic ZnO(1010) surface by using first-principles density-functional theory and nonempirical embedding methods. It turns out that the in-plane variation of the molecule-substrate interaction energy and the bonding dipole in the vertical direction are linked up by a linear relationship originating from the electrostatic coupling of the molecule with the periodic dipolar electric field generated by the Zn-O surface dimers. Long oligomers with a highly axial π-electron system such as sexiphenyl become well oriented with alignment energies of several 100 meV along rows of a positive electric field, in full agreement with recent experiments. These findings define a new route towards the realization of highly ordered self-assembled arrays of oligomers or polymers on ZnO(1010) and similar surfaces.
The Journal of Physical Chemistry C · 23 Zitationen · DOI
We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift Δ[Formula: see text] <i><sub>m</sub></i> is mainly caused by dispersion effects and depends sensitively on the molecule's specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide Δ[Formula: see text] <sub><i>m</i></sub> = -<i>QW</i><sub><i>m</i></sub> in two factors, where <i>Q</i> depends only on the molecular species and accounts for all nonresonant electronic transitions contributing to the dispersion while <i>W</i><sub>m</sub> is a geometry factor expressing the site dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI).
Physical review. B, Condensed matter · 23 Zitationen · DOI
The optical properties of quaterthiophene (4T) films have been studied and related to the presence of perfectly crystalline and orientationally disordered domains. The translational order is always retained, however, since 4T molecules lack a reflection symmetry plane perpendicular to the long molecular axis, each molecule can assume two nonequivalent orientations. The electronic state energies are almost configuration independent, but the selection rules for the transition from the first excited state towards the ground state are completely different in well-oriented and orientationally disordered domains. All observed photoluminescence spectral features of high-quality films are interpreted in terms of intrinsic emissions. The model of chiral and achiral pinwheel aggregates provides theoretical support to this picture.
Applied Physics Letters · 22 Zitationen · DOI
We report on extreme low-temperature growth of ZnO by plasma-assisted molecular beam epitaxy. Epilayers and quantum well (QW) structures with very good structural and optical properties are prepared at substrate temperatures as low as 50 °C. The growth proceeds in a single crystalline layer-by-layer mode. ZnO QWs prepared on a-plane sapphire show bright excitonic luminescence with a very narrow linewidth of only 6 meV at 5 K. High-resolution transmission electron micrographs confirm that low-temperature single crystalline growth is not restricted to a particular surface termination of ZnO but works also for crystal growth along a nonpolar direction.
Synthetic Metals · 22 Zitationen · DOI
Kooperationen5
Bestätigte Forscher↔Partner-Paare aus HU-FIS — Gold-Standard-Positive für das Matching.
SFB 951/3: Elektronische Kopplung in anorganisch/organischen Halbleiterhybridstrukturen für opto-elektronische Funktionen (TP B03)
university
SFB 951/3: Elektronische Kopplung in anorganisch/organischen Halbleiterhybridstrukturen für opto-elektronische Funktionen (TP B03)
other
SFB 951/3: Elektronische Kopplung in anorganisch/organischen Halbleiterhybridstrukturen für opto-elektronische Funktionen (TP B03)
other
SFB 951/3: Elektronische Kopplung in anorganisch/organischen Halbleiterhybridstrukturen für opto-elektronische Funktionen (TP B03)
university
SFB 951/3: Elektronische Kopplung in anorganisch/organischen Halbleiterhybridstrukturen für opto-elektronische Funktionen (TP B03)
university
Stammdaten
Identität, Organisation und Kontakt aus HU-FIS.
- Name
- PD Dr. Sylke Blumstengel
- Titel
- PD Dr.
- Fakultät
- Mathematisch-Naturwissenschaftliche Fakultät
- Institut
- Institut für Physik
- Arbeitsgruppe
- Experimentelle Physik, Hybride Bauelemente
- Telefon
- +49 30 2093-82527
- HU-FIS-Profil
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- Zuletzt gescrapt
- 26.4.2026, 01:02:51