Matthijs P. de Haas

Bio: Matthijs P. de Haas is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Charge carrier & Nanosecond. The author has an hindex of 35, co-authored 84 publications receiving 3891 citations.

Highly mobile electrons and holes on isolated chains of the semiconducting polymer poly(phenylene vinylene)

Abstract: The nature of the charge carriers in ‘conducting’ polymers is of considerable interest at present1,2, largely on the basis of the technological potential of these materials for use as the semiconducting layer in field-effect transistors (FETs) and the emissive layer in light-emitting diodes3 (LEDs). One of the main outstanding questions concerns the relative importance of intra- versus inter-chain charge transfer in determining the overall rate of charge transport. Here we apply the pulse-radiolysis time-resolved microwave conductivity technique4 to dilute solutions of a soluble dialkoxy derivative of the semiconducting polymer poly(phenylene vinylene), PPV, by which means we determine the one-dimensional intra-chain mobilities of electrons and holes on isolated polymer chains free from inter-chain interactions. The values so obtained—0.5 and 0.2 cm2 V−1 s−1 respectively—are considerably larger than the mobilities measured previously for bulk PPV-based materials5,6,7,8,9. This suggests that considerable improvement in the performance characteristics (in particular switching time and maximum current) of organic FET and LED devices should be possible if material purity and structural order can be better controlled.

Efficient intermolecular charge transport in self-assembled fibers of mono- and bithiophene bisurea compounds

Abstract: Hydrogen bonds between urea units allow self-organization of π systems in mono- and bithiophenes into fibers as shown schematically. In these fibers there is a surprisingly high mobility of charge carriers as determined by pulse-radiolysis time-resolved microwave conductivity measurements.

Photon-induced molecular charge separation studied by nanosecond time-resolved microwave conductivity

Abstract: The application of the time-resolved microwave conductivity (TRMC) technique to the quantitative measurement of charge separation in flash-photolysed molecular systems is desecribed. The apparatus required, background theory and problems involved in deriving absolute values related to the charge-separation process are fully discussed. The use of the technique is illustrated by experiments carried out on the flash photolysis of 4-dimethylamino-4′-nitrostilbene (DMANS) in several solvents. Values of the dipole moments of the T 1 and S 1 states have been estimated and for S 1 are in good agreement with literature values derived in other ways. Other parameters important to the understanding of the photophysics of DMANS are also derived.

Charge migration in supramolecular stacks of peripherally substituted porphyrins

Abstract: PORPHYRIN derivatives play a central part in energy- and electron-transfer processes in natural systems, in which they occur as individual entities or, commonly, as oligomers or supramolecular assemblies. These compounds have also been proposed for use in conducting and photoconducting bulk materials and as conductive and capacitive elements in molecular electronic devices. Much effort has therefore been devoted towards understanding the factors that control energy and charge transport within porphyrin assemblies. Here we describe studies of charge migration along one-dimensional columnar stacks of porphyrin molecules bearing peripheral hydrocarbon groups. In both the solid phase and the relatively plastic liquid-crystalline mesophase, in which the hydrocarbon groups are mobile, charge is transferred between adjacent porphyrin groups with a jump time of a few picoseconds or less. The isotropic liquid phase, on the other hand, is not conductive. The formation of supramolecular structures therefore seems to be necessary to support and direct charge and energy migration in these systems.

Charge mobilities in organic semiconducting materials determined by pulse-radiolysis time-resolved microwave conductivity: π-bond-conjugated polymers versus π-π-stacked discotics

Abstract: A review is given of the one-dimensional, intrachain and intracolumnar, charge mobilities, Σμ1D, determined for π-bond-conjugated polymeric and for π−π-stacked columnar discotic materials using the pulse-radiolysis time-resolved microwave conductivity technique. The largest values, on the order of 10 cm2/(V s), are found for single-crystal polydiacetylenes polymerized either thermally or with low doses of radiation. Much lower values of Σμ1D, covering the range from 0.009 to 0.125 cm2/(V s), are found for solution-synthesized conjugated polymers for which six different backbone structures have been investigated. This is attributed mainly to their complex morphology and the resulting static disorder in the backbone structure. The highest mobilities for this class of material, ca. 0.1 cm2/(V s), are found for liquid crystalline derivatives of polyfluorene and poly(phenylenevinylene). Larger mobilities are found for discotic materials, with maximum values close to 1 cm2/(V s) in both the crystalline solid an...

Charge transport in organic semiconductors.

Abstract: 2.2. Materials 929 2.3. Factors Influencing Charge Mobility 931 2.3.1. Molecular Packing 931 2.3.2. Disorder 932 2.3.3. Temperature 933 2.3.4. Electric Field 934 2.3.5. Impurities 934 2.3.6. Pressure 934 2.3.7. Charge-Carrier Density 934 2.3.8. Size/molecular Weight 935 3. The Charge-Transport Parameters 935 3.1. Electronic Coupling 936 3.1.1. The Energy-Splitting-in-Dimer Method 936 3.1.2. The Orthogonality Issue 937 3.1.3. Impact of the Site Energy 937 3.1.4. Electronic Coupling in Oligoacene Derivatives 938

Semiconducting π-conjugated systems in field-effect transistors: a material odyssey of organic electronics.

Abstract: Since the discovery of highly conducting polyacetylene by Shirakawa, MacDiarmid, and Heeger in 1977, π-conjugated systems have attracted much attention as futuristic materials for the development and production of the next generation of electronics, that is, organic electronics. Conceptually, organic electronics are quite different from conventional inorganic solid state electronics because the structural versatility of organic semiconductors allows for the incorporation of functionality by molecular design. This versatility leads to a new era in the design of electronic devices. To date, the great number of π-conjugated semiconducting materials that have either been discovered or synthesized generate an exciting library of π-conjugated systems for use in organic electronics. 11 However, some key challenges for further advancement remain: the low mobility and stability of organic semiconductors, the lack of knowledge regarding structure property relationships for understanding the fundamental chemical aspects behind the structural design, and realization of desired properties. Organic field-effect transistors (OFETs) are a kind of device consisting of an organic semiconducting layer, a gate insulator layer, and three terminals (drain, source, and gate electrodes). OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but they also provide an important insight into the charge transport of πconjugated systems. Therefore, they act as strong tools for the exploration of the structure property relationships of πconjugated systems, such as parameters of field-effect mobility (μ, the drift velocity of carriers under unit electric field), current on/off ratio (the ratio of the maximum on-state current to the minimum off-state current), and threshold voltage (the minimum gate voltage that is required to turn on the transistor). 17 Since the discovery of OFETs in the 1980s, they have attracted much attention. Research onOFETs includes the discovery, design, and synthesis of π-conjugated systems for OFETs, device optimization, development of applications in radio frequency identification (RFID) tags, flexible displays, electronic papers, sensors, and so forth. It is beyond the scope of this review to cover all aspects of π-conjugated systems; hence, our focus will be on the performance analysis of π-conjugated systems in OFETs. This should make it possible to extract information regarding the fundamental merit of semiconducting π-conjugated materials and capture what is needed for newmaterials and what is the synthesis orientation of newπ-conjugated systems. In fact, for a new science with many practical applications, the field of organic electronics is progressing extremely rapidly. For example, using “organic field effect transistor” or “organic field effect transistors” as the query keywords to search the Web of Science citation database, it is possible to show the distribution of papers over recent years as shown in Figure 1A. It is very clear

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Functional Supramolecular Polymers

Abstract: Supramolecular polymers can be random and entangled coils with the mechanical properties of plastics and elastomers, but with great capacity for processability, recycling, and self-healing due to their reversible monomer-to-polymer transitions. At the other extreme, supramolecular polymers can be formed by self-assembly among designed subunits to yield shape-persistent and highly ordered filaments. The use of strong and directional interactions among molecular subunits can achieve not only rich dynamic behavior but also high degrees of internal order that are not known in ordinary polymers. They can resemble, for example, the ordered and dynamic one-dimensional supramolecular assemblies of the cell cytoskeleton and possess useful biological and electronic functions.