zum Inhalt springen

Collaborative Research Projects

The individual PhD projects are based on collaborative research projects between Canadian and German partners. All projects specify research collaborations, which exploit interdisciplinary approaches to investigate highly relevant questions in current research related to organic electronics. Emphasis is put on training using advanced research instrumentation, which in each PhD thesis provides the student with the infrastructure at her/his home institution as well as the partner facilities abroad. This opportunity constitutes truly an added value, since it cannot be matched by a regular PhD thesis in a non-structured graduation program.

Overview German Projects






Working Title

Principle Investigators (PIs)






Photoactive metal complexes constructed with novel polypyridine ligands

Luetzen (GER)

Hanan (CAN)






Coordination Polymers and MOFs with High Charge Carrier Mobility

Ruschewitz (GER)

Fricsic (CAN)

Perepichka (CAN)





Polaron confinement in molecular architechtures

Schmidt (GER)

Perepichka (CAN)

Meerholz (GER), Schiemann (GER), Loosdrecht (GER)





Hybrid DNA assembled 3D plasmonic nanostructures for modified light matter interaction

Lindfors (GER)

Sleiman (CAN)

Linden (GER)

Meerholz (GER)





Metal?organic frameworks based on nanoscale molecular spoked wheels

Höger (GER)

Wuest (CAN)






Polaronic excitation in organic matter

Loosdrecht (GER)

Siwick (CAN)






Charge generation in organic OPVs

Loosdrecht (GER)

Silva (CAN)






Filamentary charge transport in organic semiconductors

Meerholz (GER)

Grütter (CAN)






Electronic structure and transport properties of graphitic intercalation compound bilayers with light and heavy alkali atoms

Grüneis (GER)

Szkopek (CAN)

Busse (GER)





Covalent network formation in supramolecular Archimedean patterns of shape-persistent molecules on solid surfaces

Jester (GER)

Rosei (CAN)

Höger (GER)





hBN layers as substrates for self-organized organic molecules

Sokolowski (GER)

Siaj (CAN)

Busse (GER)





Vertical organic transistors with contact switching

Meerholz (GER)

Martel (CAN)

Cicoira (CAN)





The role of spins in OE devices

Schiemann (GER)

Organic chemist (CAN)

Meerholz (GER)

Loosdrecht (GER)?





Understanding and controlling the thin film formation of small molecule semiconductors

Olthof (GER)

Martel (CAN)

Meerholz (GER)






Meerholz (GER)

Grütter (CAN)

Soergel (GER)






Mathur (GER)

??? (CAN)



Overview Canadian Projects






Working Title

Principle Investigators (PIs)






3D conjugated polymer nanoparticles

Perepichka (CAN)

Schmidt (GER)

Cosa (CAN)

Meerholz (GER)





The Multicomponent synthesis of pi-conjugated polymers: tunable and efficient routes to polymer-based electronic devices

Arndtsen (CAN)

Meerholz (GER)






Novel MOLEDs constructed with bis-hydroxyamidine ligands and Zn(II) ions

Hanan (CAN)

Lützen (GER)

Meerholz (GER)





Fabrication of OLED and/or OPV by surface-initiated polymerization

Skene (CAN)

Meerholz (GER)






Confinement of molecules in CNT

Martel (CAN)

Meerholz (GER)

Lützen (GER)





Exciton dynamics in organic semiconductors (photonic/cavity)

Silva (CAN)

Loosdrecht (GER)






Characterization of electronic structure of 2D polymeric materials

Rosei (CAN)

Olthof (GER)

Perepichka (CAN)

Meerholz (GER)

Busse (GER)





UV optoelectronic properties of CVD-grown hBN

Szkopek (CAN)

Grüneis (GER)

Siaj (CAN)





Quantum dots of 2D-materials

Grütter (CAN)

Michely (GER)

Busse (GER)





Controlled polymerization and DNA-self-assembly of hole-transport molecules

Sleiman (CAN)

Meerholz (GER)







Wuest (CAN)

Höger /Jester (GER)







Kena-Cohen (CAN)

???? (GER)




This research is directed towards developing efficient methods to synthesize and tune pi-conjugated polymers for use in electronic materials application.  Conjugated polymers have emerged over the past several decades as key components for a range of applications.  Nevertheless, their synthesis, structural tuning and ultimate production present major challenge, as they are typically the product of a long, multistep sequence.  We propose to develop a method to assemble conjugated polymers in one step from combinations of available building blocks and with minimal waste (a multicomponent polymerization).  This will provide a Green approach to conjugated polymers, allow access to new classes of reactive electronic materials (e.g. poly-1,3-dipoles), and, due to its modular nature, provide the ability to tune these polymers to modulate their properties.  These features will be exploited to control the electronic properties, 2D and 3D ordering, cross linking, create hybrid donor/acceptor materials, and effect other physical properties of the materials.


Graphite intercalation compounds (GICs) have been studied extensively but new developments have emerged requiring a revisit: exfoliation and CVD synthesis to reach the 2D bilayer limit, the advent of higher B/T ratios, and the great theoretical interest in spin-orbit coupling relating to topology. In this project we will prepare and characterize GICs with various intercalant atoms. We will investigate them by ARPES and Raman and electron transport under high magnetic field and low. We will address the following questions:

1)do heavy alkali atoms impart a strong spin-orbit coupling in few-layer GICs?

2)do Shubnikov-de Haas oscillations above the critical field tell us about superconductivity in GICs?

3)can a bandgap be tuned in GIC bilayers with an applied electric field?

4)is there any signature – such as a zero-bias anomaly - of theoretically predicted Bose-Einstein condensates in GIC bilayers?


Filamentary charge transport in organic semiconductors:

Klaus – please add some intro stuff/motivation.

We will use combined atomic force and Kelvin probe force microscope techniques to determine the presence of hotspots on samples exposed to different intensities of light. The nature of the transport will be deteremined by performing these measurements as a function of temperature. 

Quantum dots of 2D-materials

Quantum mechanical confinement energy level structures can be measured by recently developed atomic force microscopy techniques in the Grutter lab. The Micheley group can grow graphene quantum dots of different shapes and characterize them using low-T STM spectroscopy methods. We will combine the AFM and STM techniques on the same samples to understand in detail how the 2D geometry of the graphene quantum dot relate to its confinement potential shape.  


Project 2 Luetzen and Hanan

The design and synthesis of photoactive metal complexes requires complete control over the catalytic preparation of the ligands used in the complexes. The Luetzen group has devised novel and effective methods to produce previously unknown polyheterocyclic ligands. These ligands will be converted into photoactive metal complexes by the Hanan group, and their photoactivity will be evaluated. The best candidates will be incorporated into molecular devices.


Project 9 Hanan and Luetzen

Hydroxyamidines are a new class of bidentate ligands that exhibit strong metal binding properties. New polytopic hydroxyamidine ligands will be prepared by the Hanan group and their incorporation into larger polymetallic assemblies will be accomplished by the Luetzen group. The optoelectronic properties of the new supramolecular assemblies will be verified by electronic absorption and emission spectroscopies, and their incorporation into functional devices will be accomplished in conjunction with the Meezholz group.


Shape-persistent spoked wheel compounds will be decorated with extraannular metal-binding sites (e.g. pyridines) in order to obtain well defined- metal-organic superstructures with variable dimensionality. These can be used to pattern surfaces (HOPG) that can be investigated by means of STM and AFM (together with S. Jester, Bonn) or act as porous metal-organic frameworks. It will be also of interest to evaluate the effect of the dimensionality on the optical or electrooptical properties of the materials.

Jester (#24)

Organic molecules that are adsorbed on a metal substrate under ultra-high vacuum conditions may form covalent bonds between adjacent functional units as an effect of a reaction catalysis by diffusing single adatoms. This requires that the reactive groups are arranged in an appropriate relative geometry. The ultimate aim is a covalent 2D network formation of several molecules from a self-assembled monolayer. Their packing control, however, is a challenge itself. A more predictable approach to study the covalent bond formation in detail relies on a covalent template architecture in which the reactive groups are intramolecularly connected. The project focuses on the synthesis and scanning tunneling microscopy investigation of arylene and arylene-alkynylene structures with pre-oriented functional units that are designed to form C–C bonds after their deposition onto the metal surface. We will relate the results to our solution chem­istry of highly strained bicyclophane compounds.


Increasing quantum efficiency using strong exciton-phonon-photon coupling

Strong exciton-photon interaction and exciton-phonon interactions are common in pi-conjugated materials. The first results from their large oscillator strength, while the second is due to the strong dependence of the excited-state energy on the nuclear configuration. In optical microcavities, strong exciton-photon interaction can be harnessed to create h­­ybrid states called polaritons with nearly 100% emission efficiency. The challenge, however, is to find an effective way to populate the states. One mechanism is via exciton-phonon coupling, whereby an excited exciton can scatter into a polariton. This scattering mechanism can be much faster than typical non-radiative decay. One can thus engineer devices where scattering into efficient polaritonic states can overcome losses. In effect, creating good emitters with conventionally non-emissive species.

Single-photon OLEDs based on isolated polymer chains

In the past decade, single-molecule spectroscopy has unveiled important information about the interactions of isolated molecules with their host matrix, intersystem crossing, photobleaching, static disorder and diffusion. The realization of single-emitter organic light-emitting diodes, however, has proved difficult due the presence of dark long-lived triplets. One solution based on the use of phosphorescence has been investigated, but it is ultimately limited by the slow decay rate of phosphorescent emitters. A novel alternative would be to use Förster transfer to polymer chains where intersystem crossing is hampered. Wrapping polymer chains with cyclodextrin (e.g. sugar) molecules has proved successful for this. We propose to use this approach to create efficient sources of single-photons with repetition rates only limited by the singlet lifetime (GHz). In addition to shedding light on the local environment, these would have applications as efficient sources for quantum cryptography and quantum information.

Exciton diffusion in organic monolayers and wires

A variety of methods have been proposed to measure exciton diffusion. Most of these methods are steady-state measurements that rely either on a sensitizing layer or fluorescence quenching. Meanwhile, ultrafast methods typically involve measuring the bimolecular annihilation rate and then making a number of (often incorrect) modeling assumptions. A recent method has been proposed to directly measure diffusion simultaneously in space and time using time-correlated single photon counting. Most importantly, it allows this measurement can distinguish between diffusive and dispersive transport. We propose to improve on this method, by completely eliminating moving parts and using a streak camera in its imaging configuration for detection. We will apply the technique model 2D and 1D organic systems to directly study the effect of dimensionality and disorder on transport within these systems.



We use DNA based assembly of photonic nanostructures to study light-matter interaction in three-dimensional (3D) nanoplasmonic structures. The goal is to design, fabricate, and characterize hybrid plasmonic materials that combine plasmonic nanostructures with light emitting moieties. In particular, we will study 3D structures where both the electric and magnetic near-field distributions can be engineered to obtain electric or magnetic resonances as well as strong chiral fields. Key scientific questions and tasks are: mapping the modes of 3D DNA nanoplasmonic structures, design and fabrication of structures with magnetic resonances or strong chiral fields in the visible spectral range, and enhancing magnetic dipole and other higher-order transitions using nanoplasmonics.

Antenna-coupled nano-OLEDs

One of the key topics in nano-optics is developing bright and stable single photon sources. They have applications in quantum information science, spectroscopy and imaging. An ideal single photon source should be electrically driven allowing single electrons to be efficiently converted into single photons.


In this project we combine directional optical antennas with nanoscale organic light emitting diodes (OLEDs). The OLED is coupled to an optical antenna, which increases the radiative decay and directs the emission in the desired direction. Our goal is to decrease the size of the OLED to a single polymer chain, which emits single photons via the optical antenna.




Charge transport in organic conjugated systems is more often than not carried by polaronic excitations. The nature of these excitations is not always very well understood, partially because experimentally it is often difficult to separate these states from other states such as impurity bound states and charge transfer states. This project uses a variety of ultrafast pump-probe techniques, including transient UV-VIS absorption, transient grating, transient Raman, and transient mid- and far-infrared spectroscopy to elucidate the nature, formation, and decay dynamics of polaronic states.


Charge generation in organic photovoltaic (OPV) materials depends crucially on the nature of interfacial charge transfer states. The mechanisms of charge transfer state dissociation and recombination strongly influence the efficiency of OPV devices. The project focuses on the branching ratio of charge transfer state dissociation/recombination as well as the optical manipulation of this ratio. For that a variety of ultrafast optical techniques (often of the pump-push-probe type) will be used, including transient grating, time resolved Raman and electrical/luminescence detected two dimensional spectroscopy.


Project 2 (T1) Lützen, Hanan, (Meerholz)

Photoactive metallosupramolecular complexes constructed from novel oligopyridine ligands

Within this project principles of metallosupramolecular chemistry will be used to arrange p-conjugated oligomeric building blocks in a well-defined manner to affect their optoelectronic properties. Therefore, oligopyridine ligands will be synthesized that either use a p-conjugated oligomeric building block to bridge the metal binding pyridines or will be equipped with p-conjugated systems in their periphery. Upon coordination to suitable metal ions these ligands self-assemble into two-dimensional macrocyclic or three-dimensional cage-like metallosupramolecular aggregates which present the p-conjugated systems in a well defined manner.

Project 9 (T1) Hanan, Lützen, (Meerholz)

Novel MOLEDs constructed with bis(hydroxyamidine) ligands and Zn(II) ions

Within this project new bis(hydroxyamidine) ligands will be prepared and used to form photoactive zinc(II) complexes. These will be implemented as active components into novel types of metal organic light emitting diodes (MOLEDs).

(hopefully, Garry will give some more input, concerning the classification in T1-3, I would suppose that it also goes into T1 but maybe Garry has something else in mind)

Project 20 (T1) Martel, Lützen, (Meerholz)

Confinement of molecules in carbon nanotubes

Carbon nanotubes will be used as a kind of porous template to orientate p-conjugated oligomers in a defined linear arrangement. Therefore, the carbon nanotubes will be filled by symmetric and non-symmetric p-conjugated oligomers consisting of phenylene, phenyleneethynylene, oligothiophene, carbazole units and hybrids of them to achieve a well-defined one-dimensional array of these materials within the confined arrangement of the nanotubes and study their optoelectronic behavior.

(hopefully, Richard will give some more input, concerning the classification in T1-3, I would suppose that it goes either into T1 or T3)


1D Confinement of dye molecules inside CNT

R. Martel (CAN), Lützen (GER) and Co-PI: Klaus Meerholz (GER) 

The optical properties of dye molecules encapsulated inside single-walled carbon?nanotubes (SWNTs) will be investigated using Raman and fluorescence spectroscopies. Recent experiments performed on rod-like dyes, such as alpha-sexithiophene, assembled inside individualized SWNTs revealed non-linear effects and resonant Raman cross-section (CS) of (3±2)x10-21 cm2/sr, which are unexpectedly large. These enhanced properties in Raman enable detection of individual molecular aggregates at the highest optical resolution. Free from fluorescence background?and photobleaching, this Raman effect allows robust detection capabilities at a spatial resolution beyond the limit of Raman?microscopes. The unique optical sensitivity will be used to probe the encapsulation process from solution of different dyes inside an individual SWNT. The experiments will also investigate possible ways to further enhance the non-linear responses and explore energy transfer effects between the nanotube and the dye molecules.

Vertical organic transistors with contact switching

R. Martel (CAN), F. Cicoira (CAN) and Klaus Meerholz (GER)

Develop p- and n-type organic-nanotube field-effect transistors: This is a vertical field-effect transistor structure in which the main active element is a Schottky junction between CNTs and a layer of OS. The structure is composed of stacks of Organic Semiconductors (OSs) disposed vertically in a way to ensure gating from the bottom gate structure located underneath a source contact made of a nanotube network. The stacks consists of layers of low-doped to highly doped OS deposited on top of the CNT network, followed by an engineered multilayer drain conductor. The CNT layer can be printed or deposited from solution in an area defined lithographically on top of the gate stack structure (i.e. a metal-dielectric layer) and then connected on the side using a metal source contact. 

•        Scientific question : Develop low power switches for complementary electronics using disposable and printable nanotube-organic materials. The main challenge is to develop a fabrication procedure that is compatible with printing processes

•        What will the student do during her/his exchange (min. 6 months)? 

Montreal: Develop carbon nanotube network structures (metallic and semiconducting) and new methods of deposition. 

Cologne: Develop the organic layer materials for the stack with p-type and n-type transport properties and method of deposition.

The student will (i) fabricate electronic nano-devices using micro/nano fabrication tools (e-beam lithography, clean room facility), (ii) characterize and optimize their electrical performances in relation with the circuit learning-rules and scaling requirements, (iii) study in depth the physical mechanisms at play. 

•        What is the gain from the GER-CAN collaboration as opposed to doing the same research at home? 

These labs provide wide and complementary expertise on nanotube (Montreal) and organic (Cologne) materials for transistors. We will blend knowledge from both labs to prepare low power devices operating below 5V for use in sensors or printable electronics.


Abstract for Understanding and controlling the thin film formation of small molecule semiconductors

In this project the growth of thin films of organic semiconductors, especially merocyanine layers, will be studied, ranging from sub-monolayer thickness up to several nanometers. The influences of substrate, preparation condition, annealing, and additives on the film formation (growth mode, ordering, and crystallinity) as well as the energy levels (injection barriers, trap density, chemical shifts) will be investigated. This will be done by combining spectroscopic measurement techniques of UV- and X-ray photoelectron spectroscopy (UPS/XPS) and Raman spectroscopy with structural characterization methods of low energy electron microscopy (LEEM), grazing incident x-ray diffraction (GIXRD), scanning tunneling microscopy (STM), and atomic force microscopy (AFM).


Electronic Structure of 2D poylmeric materials

Much attention has been given to 2-dimensional conjugated polymers during the last several years several years, but our present understanding of these materials is derived primarily from structural and morphological characterizations. Their anticipated utility largely comes from the fact that they will retain bandgaps dictated by the design of the building blocks while at the same time exhibiting high charge mobility, on par with graphene, due to their high degree of conjugation. The project centers on the study of the electronic structure of these materials by means of high-resolution scanning probe microscopy and angle-resolved photoelectron spectroscopy.


Up to now only very few MOFs (metal-organic frameworks) with high charge mobility are known. In this proect several different synthetic approaches shall be followed to synthesize novel conducting coordination polymers (CPs) and MOFs:

·      Charge mobility via SS contacts in CPs/MOFs with S containing ligands

·      Embedment of redox-active, conjugated guests in MOF matrices

·      CPs/MOFs based on second- and/or third-row transition metals, redox-active linkers/cores and hetero-bimetallic structures

The new compounds shall be structurally characterized by XRD (single crystal and powder) and the physical properties of the new systems will be investigated in cooperation with other groups of the network. After successful synthesis of bulk materials the fabrication of thin films shall also be attempted.



The ubiquitous natural pigment eumelanin is studied for its photoprotective, thermoregulating, free-radical scavenging, and anti-oxidant functions in the human body. Eumelanin also exhibits a set of physicochemical properties including strong broad-band UV-Vis absorption, metal chelation properties. At present it is investigated as a potential mixed electronic-ionic conductor.


·        How eumelanin polymers self assemble to form thin films (amenable to device applications)?

·        How does proton conduction take place in eumelanin thin films? Are there water channels (similar to what happens in Nafion) in eumelanin?

·        Is electronic conduction possible in eumelanin? If so, on which scale: nanoscale, microscale?

·        What is the contribution of reversible and irreversible electrochemical processes to the electrical current measured when thin eumelanin films are included between metal electrodes?


Hexagonal boron nitride (hBN), also known as white graphite, is a wide bandgap semiconductor that has found use as a high quality dielectric in van der Waals heterostructures incorporating other 2D materials such as graphene. Recently, we observed quadratic scaling of current with voltage, consistent with space-charge limited transport with a mobility of up to ~ 0.01 cm2/Vs.  We suggest that h-BN can function as a semiconductor with appropriately chosen contact electrodes. Based in this work, the aim of the present project is to test out the possibility to use h-BN films as interfaces in organic electronic devices, e.g., organic field effect transistors (OFETs), organic light emitting devices (OLEDs), and organic solar cells (OSCells). For this purpose the project will interlink the above noted two experimental groups.


Exploring polaron confinement in molecular architechtures

Annette M. Schmidt, Dmitry Perepichka

The spin state of an electron is currently achieving increasing awareness as an additional degree of freedom in electronic devices, and is of high interest for future data storage devices, spin injection and magnetoresistance. The related phenomena recently observed in metal-free conjugated polymers deserve a thorough investigation. The project aims at the investigation of the intrinsic structural requirements for the influence of dimensionality and symmetry on the spin interaction in metal-free 1D (linear), 2D (branched) and 3D (intercrosslinked) thiophene-based polymers with systematically varied p-electron structure.


Design and evaluation of 3D conjugated polymer nanoparticles

Dmitry Perepichka, Annette M. Schmidt

Covalently linked organic solids (metal-organic frameworks (MOF), covalent organic frameworks (COF), and microporous polymers) represent a rapidly growing field of materials science. p-conjugated structural units in such materials creates an exciting opportunity to develop novel semiconductors with unprecedentedly strong (for organics) 3D electronic coupling. The permanent porosity in such materials could enable applications in sensing and energy storage. However, a number of high-tech applications are impeded by the lack of processability of such materials, generally produced as intractable powders. Inspired by the example of inorganic semiconducting quantum dots, we wish to develop semiconducting COF/microporous polymers nanoparticles of controlled size and solubility.


Typically, conjugated polymers are prepared such that they are solution processable.  This is to ensure that their properties can be evaluated using conventional solution techniques.  While solution processable polymers have many advantages, their synthesis including that of the corresponding monomers is complicated. The goal of the collaborative project is the in situ polymerization of conjugated polymers within devices and to validate their use for simplifying device fabrication.  This approach offers many advantages in terms of polymer preparation and device fabrication. Most importantly, polymers with desired properties can be identified by high throughput screening.  The applicability of this alternative process for electronic applications, including OLEDs and OPVD will be examined.  Implementing this production into large scale applications will also be examined.


Structure-function relationships in organic films studied by a combined spectroscopy and transport approach

It is well known that the preferred orientation of a given vacuum sublimated organic molecule depends strongly on the substrate and on the film thickness. One of the standard methods to determine the orientation is near edge x-ray absorption fine structure spectroscopy (NEXAFS). This method relies on the fact that the transitions from core-levels to unoccupied states have a strong polarization dependence. This makes NEXAFS in combination with techniques to determine layer thickness a powerful spectroscopic method for characterization of the morphology and the electronic structure of organic molecules. We will extend the power of this method by combining it with electronic transport measurements, allowing us to elaborate on the correlation between molecular ordering and charge transport properties. In the proposed research project organic, films in a field effect transistor geometry will be studied versus temperature and magnetic field. This would allow us to study the effects of molecular order on the charge transport in van der Waals crystals, and extend the work seamlessly to the development of novel organic electronic devices.


Sleiman/Meerholtz Project

Inspired by biological polymers, sequence-controlled synthetic polymers are highly promising materials that integrate the robustness of synthetic systems with the information-derived activity of biological counterparts. We recently reported a solid-phase approach to generate completely monodisperse and sequence-defined polymers conjugates using readily available reagents (Angew. Chem. 2014).  We propose to use this method and incorporate a variety of conjugated molecules as building blocks.  This will yield a new class of conjugated sequence-defined polymers.  These molecules have the particularity of being punctuated by phosphate groups repeating in the polymer, thus offering amphiphilic self-assembly modes and resulting electronic properties that are dependent on the sequence of the polymer.  


hBN layers as substrates for self-organized layers of organic molecules

Monoatomic and ultraflat layers of hexagonal boron nitride (hBN) will be grown on different metal surfaces (e.g., Ag(111), Cu(111)) in a self-terminating catalytic process by dosing of borazine. Structural properties of these hBN layers will be investigated by  scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). In a second step large ? conjugated organic molecules will be deposited on the hBN films. The formations of islands, clusters, and closed films of these molecules on the hBN layer is of interest. In particular, molecules which form semiconducting films or which are fluorescent will be considered. For the latter we plan to perform fluorescence spectroscopy experiments at low temperatures. The questions of the project are: Does the hBN layer lead to electronic decoupling of the molecules from the metal substrate? What is the influence of a possible structural and electronic corrugation of the hBN on the growth of the molecular aggregates? Can one optimize thin semiconducting organic film devices by introduction of hBN layers at interfaces to the electrodes?