Carrier Transport (carrier + transport)

Distribution by Scientific Domains

Kinds of Carrier Transport

  • charge carrier transport


  • Selected Abstracts


    Temperature-Resolved Local and Macroscopic Charge Carrier Transport in Thin P3HT Layers,

    ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
    Patrick Pingel
    Abstract Previous investigations of the field-effect mobility in poly(3-hexylthiophene) (P3HT) layers revealed a strong dependence on molecular weight (MW), which was shown to be closely related to layer morphology. Here, charge carrier mobilities of two P3HT MW fractions (medium-MW: Mn,=,7,200 g mol,1; high-MW: Mn,=,27,000 g mol,1) are probed as a function of temperature at a local and a macroscopic length scale, using pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) and organic field-effect transistor measurements, respectively. In contrast to the macroscopic transport properties, the local intra-grain mobility depends only weakly on MW (being in the order of 10,2 cm2 V,1 s,1) and being thermally activated below the melting temperature for both fractions. The striking differences of charge transport at both length scales are related to the heterogeneity of the layer morphology. The quantitative analysis of temperature-dependent UV/Vis absorption spectra according to a model of F. C. Spano reveals that a substantial amount of disordered material is present in these P3HT layers. Moreover, the analysis predicts that aggregates in medium-MW P3HT undergo a "pre-melting" significantly below the actual melting temperature. The results suggest that macroscopic charge transport in samples of short-chain P3HT is strongly inhibited by the presence of disordered domains, while in high-MW P3HT the low-mobility disordered zones are bridged via inter-crystalline molecular connections. [source]


    Comparison of Trap-state Distribution and Carrier Transport in Nanotubular and Nanoparticulate TiO2 Electrodes for Dye-Sensitized Solar Cells

    CHEMPHYSCHEM, Issue 10 2010
    Raheleh Mohammadpour
    Abstract Dye-sensitized solar cells (DSCs) with nanotubular TiO2 electrodes of varying thicknesses are compared to DSCs based on conventional nanoparticulate electrodes. Despite the higher degree of order in one-dimensional nanotubular electrodes, electron transport times and diffusion coefficients, determined under short-circuit conditions, are comparable to those of nanoparticulate electrodes. The quasi-Fermi level, however, is much lower in the nanotubes, suggesting a lower concentration of conduction band electrons. This provides evidence for a much higher diffusion coefficient for conduction band electrons in nanotubes than in nanoparticulate films. The electron lifetime and the diffusion length are significantly longer in nanotubular TiO2 electrodes than in nanoparticulate films. Nanotubular electrodes have a trap distribution that differs significantly from nanoparticulate electrodes; they possess relatively deeper traps and have a characteristic energy of the exponential distribution that is more than two times that of nanoparticulate electrodes. [source]


    Towards Protein Field-Effect Transistors: Report and Model of a Prototype,

    ADVANCED MATERIALS, Issue 7 2005
    G. Maruccio
    A protein field-effect transistor (Pro-FET) based on the blue-copper protein azurins (see Figure) and operating at room temperature and ambient pressure is demonstrated. The transfer characteristics of the Pro-FET exhibit a pronounced resonance due to the switch from behaving as a n-metal oxide semiconductor FET (n-MOSFET) to a p-MOSFET. Carrier transport through the device is explained in terms of an equilibrium between the two possible oxidation states of the redox site (Cu1+ and Cu2+). [source]


    Carrier transport in nanodevices: revisiting the Boltzmann and Wigner distribution functions

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2009
    Fons Brosens
    Abstract In principle, transport of charged carriers in nanometer sized solid-state devices can be fully characterized once the non-equilibrium distribution function describing the carrier ensemble is known. In this light, we have revisited the Boltzmann and the Wigner distribution functions and the framework in which they emerge from the classical respectively quantum mechanical Liouville equation. We have assessed the method of the characteristic curves as a potential workhorse to solve the time dependent Boltzmann equation for carriers propagating through spatially non-uniform systems, such as nanodevices. In order to validate the proposed solution strategy, we numerically solve the Boltzmann equation for a one-dimensional conductor mimicking the basic features of a biased low-dimensional transistor operating in the on-state. Finally, we propose a computational scheme capable of extending the benefits of the above mentioned solution strategy when it comes to solve the Wigner,Liouville equation. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Carrier transport studies of dichromatic InGaN-based LEDs with spacer bandgap dependence

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
    Shih-Wei Feng
    Abstract Carrier transport of dichromatic InGaN-based LEDs with AlGaN spacer bandgap dependence has been studied. TREL measurements show that carrier dynamics could be well explained by the combined effects of carrier effective mass, carrier mobility, quantum confinement, and device structures. The experimental results provide important information for device designs. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Inkjet-Printed Single-Droplet Organic Transistors Based on Semiconductor Nanowires Embedded in Insulating Polymers

    ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010
    Jung Ah Lim
    Fabrication of organic field-effect transistors (OFETs) using a high-throughput printing process has garnered tremendous interest for realizing low-cost and large-area flexible electronic devices. Printing of organic semiconductors for active layer of transistor is one of the most critical steps for achieving this goal. The charge carrier transport behavior in this layer, dictated by the crystalline microstructure and molecular orientations of the organic semiconductor, determines the transistor performance. Here, it is demonstrated that an inkjet-printed single-droplet of a semiconducting/insulating polymer blend holds substantial promise as a means for implementing direct-write fabrication of organic transistors. Control of the solubility of the semiconducting component in a blend solution can yield an inkjet-printed single-droplet blend film characterized by a semiconductor nanowire network embedded in an insulating polymer matrix. The inkjet-printed blend films having this unique structure provide effective pathways for charge carrier transport through semiconductor nanowires, as well as significantly improve the on-off current ratio and the environmental stability of the printed transistors. [source]


    A CdSe Nanowire/Quantum Dot Hybrid Architecture for Improving Solar Cell Performance

    ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
    Yanghai Yu
    Abstract Incorporating colloidal CdSe quantum dots (QDs) into CdSe nanowire (NW)-based photoelectrochemical solar cells increases their incident-photon-to-carrier conversion efficiencies (IPCE) from 13% to 25% at 500,nm. While the effect could, in principle, stem from direct absorption and subsequent carrier generation by QDs, the overall IPCE increase occurs across the entire visible spectrum, even at wavelengths where the dots do not absorb light. This beneficial effect originates from an interplay between NWs and QDs where the latter fill voids between interconnected NWs, providing electrically accessible conduits, in turn, enabling better carrier transport to electrodes. The presence of QDs furthermore reduces the residual polarization anisotropy of random NW networks. Introducing QDs therefore addresses an important limiting constraint of NW photoelectrochemical solar cells. The effect appears to be general and may aid the future design and implementation of other NW-based photovoltaics. [source]


    High Efficiency Blue Organic LEDs Achieved By an Integrated Fluorescence,Interlayer,Phosphorescence Emission Architecture

    ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
    Tianhang Zheng
    Abstract This paper presents a new strategy to develop efficient organic light-emitting devices (OLEDs) by doping fluorescent- and phosphorescent-type emitters individually into two different hosts separated by an interlayer to form a fluorescence,interlayer,phosphorescence (FIP) emission architecture. One blue OLED with FIP emission structure comprising p -bis(p - N,N -diphenylaminostyryl)benzene (DSA-Ph) and bis[(4,6-di-fluorophenyl)-pyridinate- N,C2']picolinate (FIrpic) exhibiting a peak luminance efficiency of 15.8,cd A,1 at 1.54,mA cm,2 and a power efficiency of 10.2,lm W,1 at 0.1,mA cm,2 is successfully demonstrated. The results are higher than those of typical phosphorescent OLEDs with a single emission layer by 34% and 28%, respectively. From experimental and theoretical investigations on device performance, and the functions of the used emitters and interlayer, such enhancement should ascribe to the appropriate utilization of the two types of emitters. The fluorescent emitter of DSA-Ph is used to facilitate the carrier transport, and thus accelerate the generation of excitons, while the phosphorescent emitter of FIrpic could convert the generated excitons into light efficiently. The method proposed here can be applied for developing other types of red, green, and white OLEDs. [source]


    High-Performance Air-Processed Polymer,Fullerene Bulk Heterojunction Solar Cells

    ADVANCED FUNCTIONAL MATERIALS, Issue 22 2009
    Chang-Yong Nam
    Abstract High photovoltaic device performance is demonstrated in ambient-air-processed bulk heterojunction solar cells having an active blend layer of organic poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), with power conversion efficiencies as high as 4.1%, which is comparable to state-of-the-art bulk heterojunction devices fabricated in air-free environments. High-resolution transmission electron microscopy is combined with detailed analysis of electronic carrier transport in order to quantitatively understand the effects of oxygen exposure and different thermal treatments on electronic conduction through the highly nanostructured active blend network. Improvement in photovoltaic device performance by suitable post-fabrication thermal processing results from the reduced oxygen charge trap density in the active blend layer and is consistent with a corresponding slight increase in thickness of an ,4,nm aluminum oxide hole-blocking layer present at the electron-collecting contact interface. [source]


    Versatile, Benzimidazole/Amine-Based Ambipolar Compounds for Electroluminescent Applications: Single-Layer, Blue, Fluorescent OLEDs, Hosts for Single-Layer, Phosphorescent OLEDs

    ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009
    Chih-Hsin Chen
    Abstract A series of compounds containing arylamine and 1,2-diphenyl-1H -benz[d]imidazole moieties are developed as ambipolar, blue-emitting materials with tunable blue-emitting wavelengths, tunable ambipolar carrier-transport properties and tunable triplet energy gaps. These compounds possess several novel properties: (1) they emit in the blue region with high quantum yields; (2) they have high morphological stability and thermal stability; (3) they are capable of ambipolar carrier transport; (4) they possess tunable triplet energy gaps, suitable as hosts for yellow-orange to green phosphors. The electron and hole mobilities of these compounds lie in the range of 0.68,144,,10,6 and 0.34,147,,10,6,cm2 V,1 s,1, respectively. High-performance, single-layer, blue-emitting, fluorescent organic light-emitting diodes (OLEDs) are achieved with these ambipolar materials. High-performance, single-layer, phosphorescent OLEDs with yellow-orange to green emission are also been demonstrated using these ambipolar materials, which have different triplet energy gaps as the host for yellow-orange-emitting to green-emitting iridium complexes. When these ambipolar, blue-emitting materials are lightly doped with a yellow-orange-emitting iridium complex, white organic light-emitting diodes (WOLEDs) can be achieved, as well by the use of the incomplete energy transfer between the host and the dopant. [source]


    Interfacial Polar-Bonding-Induced Multifunctionality of Nano-Silicon in Mesoporous Silica

    ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
    Jung Y. Huang
    Abstract The optoelectronic response of a material governs its suitability for a wide range of applications, from photon detection to photovoltaic conversion. To conquer the material limitations and achieve improved optoelectronic responses, nanotechnology has been employed to arrange subunits with specific size-dependent quantum mechanical properties in a hierarchically organized structure. However, building a functional optoelectronic system from nano-objects remains a formidable challenge. In this paper, the fabrication of a new artificially engineered optoelectronic material by the preferential growth of silicon nanocrystals on the bottom of the pore-channels of mesoporous silica is reported. The nanocrystals form highly stable interface structures bonded on one side; these structure show strong electron,phonon coupling and a ferroelectric-like hysteretic switching property. A new class of multifunctional materials is realized by invoking a concept that employs semiconductor nanocrystals for optical sensing and utilizes interfacial polar layers to facilitate carrier transport and emulate ferroelectric-like switching. [source]


    The Role of OTS Density on Pentacene and C60 Nucleation, Thin Film Growth, and Transistor Performance

    ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
    Ajay Virkar
    Abstract In organic thin film transistors (OTFTs), charge transport occurs in the first few monolayers of the semiconductor near the semiconductor/dielectric interface. Previous work has investigated the roles of dielectric surface energy, roughness, and chemical functionality on performance. However, large discrepancies in performance, even with apparently identical surface treatments, indicate that additional surface parameters must be identified and controlled in order to optimize OTFTs. Here, a crystalline, dense octadecylsilane (OTS) surface modification layer is found that promotes two-dimensional semiconductor growth. Higher mobility is consistently achieved for films deposited on crystalline OTS compared to on disordered OTS, with mobilities as high as 5.3 and 2.3,cm2,V,1,s,1 for C60 and pentacene, respectively. This is a significant step toward morphological control of organic semiconductors which is directly linked to their thin film charge carrier transport. [source]


    High Ambipolar Mobility in a Highly Ordered Smectic Phase of a Dialkylphenylterthiophene Derivative That Can Be Applied to Solution-Processed Organic Field-Effect Transistors,

    ADVANCED MATERIALS, Issue 3 2007
    M. Funahashi
    A phenylterthiophene derivative that exhibits a highly ordered smectic phase around room temperature is synthesized. In the bulk of the smectic phase, ambipolar carrier transport is observed and electron mobility exceeds 0.2,cm2,V,1,s,1. Thin-film transistors (see the AFM image in the figure) are fabricated by a spin-coating method and exhibit p-type operation, a field-effect mobility of 0.02,cm2,V,1,s,1, and an on/off ratio of 106. [source]


    Influence of Dipolar Fields on the Photochemical Reactivity of Thin Titania Films on BaTiO3 Substrates

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006
    Nina V. Burbure
    The photochemical properties of TiO2 films supported on BaTiO3 were investigated to test the hypothesis that dipolar fields from a ferroelectric substrate would affect the reactivity of the supported film. Photochemical reaction products were formed on the TiO2 surface in patterns that correspond to the underlying domain structure of BaTiO3. As the film thickness increases from 10 to 100 nm, the titania more effectively screens the ferroelectric field, and the pattern of reaction products is obscured. It is concluded that dipolar fields from the ferroelectric substrate influence charge carrier transport in the film and spatially localize the reaction products. [source]


    Influence of Stabilizer Concentration on Transport Behavior and Thermopower of CNT-Filled Latex-Based Composites

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2010
    Yeon Seok Kim
    Abstract The influence of the stabilizer/SWNT ratio on the transport behavior of latex-based polymer nanocomposites is examined in an effort to improve electrical conductivity while maintaining or improving the Seebeck coefficient (i.e., thermopower). Results show that phonon and electron transport are significantly affected by tube/tube junctions, and the carrier transport across the junctions can be manipulated by altering the stabilizer concentration. Electrical conductivity of composites containing 10,wt.-% SWNT nearly doubles, becoming greater than 900,S,,m,1, by changing the SWNT:GA ratio from 1:3 to 10:1, while thermal conductivity and Seebeck coefficient remain relatively constant (near 0.25,W,,m-K,1 and 40,V,,K,1, respectively). [source]


    Compensation in boron-doped CVD diamond

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2008
    Markus Gabrysch
    Abstract Hall-effect measurements on single crystal boron-doped CVD diamond in the temperature interval 80,450 K are presented together with SIMS measurements of the dopant concentration. Capacitance,voltage measurements on rectifying Schottky junctions manufactured on the boron-doped structures are also presented in this context. Evaluation of the compensating donor (ND) and acceptor concentrations (NA) show that in certain samples very low compensation ratios (ND/NA below 10,4) have been achieved. The influence of compensating donors on majority carrier transport and the significance for diamond device performance are briefly discussed. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Si-doped GaN/AlN quantum dot superlattices for optoelectronics at telecommunication wavelengths

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006
    F. Guillot
    Abstract We report on the controlled growth of Si doped GaN/AlN quantum dot (QD) superlattices, in order to tailor their intersubband absorption within the 1.3,1.5 m telecommunication wavelengths. The QD size is tuned by modifying the amount of GaN in the QDs and the growth temperature. Silicon can be incorporated in the QDs to populate the first electronic level, without significant perturbation of the QD morphology. As a proof of the capability of these structures for infrared detection, a quantum-dot intersubband photodetector at 1.38 m with lateral carrier transport is demonstrated. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Effect of dielectric screening on the binding energies and diamagnetic susceptibility of a donor in a quantum well wire

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2006
    M. Latha
    Abstract The effect of the dielectric screening on donor binding energies in a quantum wire has been estimated. Since the screening function is shown to be significant in a few phenomena like carrier transport, and not so in a few cases like the donor binding energy calculations, five different screening functions have been used in the calculations to see their relative merits. It is observed that the dielectric function obtained by Resta using the Thomas,Fermi approximation not only gives lower estimates of the ionization energies for all well widths (L ), but also is shown to vary very rapidly with L . The other functions used are those of Hermanson and Vinsome & Richardson. Using the results of the variational calculations for the finite barrier problem, the diamagnetic susceptibility of a donor as a function of L has also been estimated. Though experimental results are not available, we have compared our results for Eion with other theoretical estimates available in the literature. The agreement is found to be good. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Microscopic study of carrier transport in the organic semiconductor zinc-phthalocyanine

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
    Joo Piroto Duarte
    Abstract Nominally undoped zinc-phthalocyanine (ZnPc) was investigated using Muon Spin Rotation (,SR) to probe microscopic carrier transport properties. The study focused on the relaxation of the positive muon's polarisation produced by spin-flip scattering with charge carriers. An energy of 71(8) meV was found for the temperature activation of carrier jumps, a value that does not match the activation energies known in ZnPc from electrical measurements, and that was attributed to a fast transport component in this material. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Impact of strain on scaling of Double Gate nanoMOSFETs using NEGF approach

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008
    A. Martinez
    Abstract The effect of biaxial strain on double gate (DG) nanoscaled MOSFET with channel lengths in the nanometre range is investigated using Non-Equilibrium Green's Functions (NEGF) simulations. The NEGF simulations are fully 2D in order to accurately evaluate the effects of strain in strongly confined channels. Starting with a 14 nm gate length DG MOSFET with a corresponding body thickness of 9 nm we scale the transistors to gate lengths of 10, 6 and 4 nm and body thicknesses of 6.1, 2.6 and 1.3 nm, respectively. The simulated ID-VG characteristics show 11% improvement in the oncurrent for the 14 nm gate length transistor due to the , valley splitting. This improvement in the on-current is due to separate contributions from the 2 fold and 4 fold valleys to the carrier transport. However, in the device with an extreme body thickness of 1.3 nm the strain has no impact on its performance because the strong confinement itself produces a large valley splitting. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Effect of electron-electron interaction on the diffusion current of spin-polarized electrons

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008
    Yutaka Takahashi
    Abstract Electron-electron interaction modifies carrier transport in the spin-polarized system. The effects are investigated in the two-dimensional electron gas in semiconductor heterostructures. We find that the diffusion currents of spin-up and spin-down electrons are reduced, compared to the non-interacting values, by the momentum exchange between spin-up and spin-down electrons through their collisions (Spin Drag), and also by the electron energy renormalization arising from the manyparticle correlations. We numerically calculate the diffusion coefficients of spin-up and spin-down electrons separately in high-quality heterostructures of GaAs at low temperatures, including the effect of finite spin life time. Our calculations show that the diffusion coefficients are reduced down to less than half of their non-interacting values. We also find the negative diffusivity at low temperatures. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Temperature dependence of photoluminescence from CdS nanoclusters formed in the matrix of Langmuir-Blodgett film

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2006
    E. A. Bagaev
    Abstract In this paper photoluminescence from CdS nanoclusters formed in the matrix of Langmuir-Blodgett film has been investigated in the temperature range 5-300 K. The photoluminescence spectrum of the nanoclusters at 300 K consists of two bands at 2.9 and 2.1 eV. Temperature dependence of the high-energy band maximum deviates from the dependence of the energy bandgap of bulk CdS. The integrated PL intensity of this band decreases with increasing temperature up to 75 K, grows in a temperature range 150-230 K, and rapidly falls at temperatures higher 230 K. The experimental data have been explained within the framework of a model of recombination of carriers considering carrier transport between CdS nanoclusters. An energy of electron traps and activation energies of nonradiative recombination have been estimated to be about 120, 4 and 100 meV, respectively. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Preface: phys. stat. sol. (c) 1/8

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2004
    Markus C. Amann
    In this special issue of physica status solidi (c) we have included 10 invited papers reviewing the current state-of-the-art and the progress achieved in materials science, semiconductor theory, novel physical mechanisms and advanced device concepts in the field of nanostructured electronic and optoelectronic semiconductor devices. All of these papers were written by previous members of the Collaborative Research Centre 348 "Nanometer-Halbleiterbauelemente: Grundlagen , Konzepte , Realisierungen" (Nanometer Semiconductor Devices: Fundamentals , Concepts , Realisations), which was funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) during the period from 1991 to 2003. In these twelve years, the researchers in this programme have carried an intense activity directed towards two main objectives. First of all, Fundamentals and Concepts of nanostructure devices and their technology were explored theoretically and experimentally including the effects of low-dimensional structures on carrier transport, optical properties and spin, as well as the enabling epitaxial and nanostructure technologies such as the cleaved-edge-overgrowth technique and the self-assembled growth of quantum dots. A second field of interest was focused towards the design and development of Novel Semiconductor Devices exploiting nanostructure technology. This comprises optical detectors and memories with nanometer lateral dimensions, microwave detectors and sources up to the 300 GHz regime, innovative tunable and surface-emitting semiconductor lasers for the wavelength range 0.9 to 2 ,m, and nitride-based resonant tunnelling diodes. Some of the device innovations have meanwhile become commercial products proving also the practical importance of this research area. The articles in this special issue relate to the projects of the last three-years' funding period from 2000 to 2003 and are organized along these two topical areas. We would like to thank the numerous reviewers for their valuable comments and the editorial staff of physica status solidi (c) for their extremely helpful support. The funding by the German Research Foundation over the full project time and the continued monitoring and advice by its representatives Dr. Klaus Wehrberger and Dr. Peter Heil are gratefully acknowledged by all previous members and co-workers of this Collaborative Research Centre. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Model of the influence of energetic disorder on inter-chain charge carrier mobility in poly[2-methoxy-5-(2,-ethylhexyloxy)- p -phenylene vinylene]

    POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2009
    Petr Toman
    Abstract The theoretical model of the inter-chain charge carrier mobility in poly[2-methoxy-5-(2,-ethylhexyloxy)- p -phenylene vinylene] (MEH,PPV) doped with polar additive is put forward. The polymer chain states of a charge carrier were calculated by means of diagonalization of a tight-binding Hamiltonian, which includes disorder in both the local energies and transfer integrals. Consequently, the inter-chain charge carrier transport is taking place on a spatially and energetically disordered medium. Because it is believed that the additive does not significantly influence the polymer supramolecular structure, the polymer conformations were simplified as much as possible. On the other hand, the energetic disorder is rigorously described. The transfer rates between the polymer chains were determined using the quasi-classical Marcus theory. The model considered the following steps of the charge carrier transport: the charge carrier hops to a given polymer chain. Then, the charge carrier thermalizes to the Boltzmann distribution over all its possible states on this chain. After that, the charge carrier hops to any possible state on one of the four nearest neighboring chains. The results showed that the inter-chain charge carrier mobility is very strongly dependent on the degree of the energetic disorder. If the energetic disorder is doubled from 0.09 to 0.18,eV, the mobility decreases by two or three orders of magnitude. Copyright 2008 John Wiley & Sons, Ltd. [source]


    Comparison of device performance and measured transport parameters in widely-varying Cu(In,Ga) (Se,S) solar cells

    PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2006
    I. L. Repins
    Abstract We report the results of an extensive study employing numerous methods to characterize carrier transport within copper indium gallium sulfoselenide (CIGSS) photovoltaic devices, whose absorber layers were fabricated by diverse process methods in multiple laboratories. This collection of samples exhibits a wide variation of morphologies, compositions, and solar power conversion efficiencies. An extensive characterization of transport properties is reported here,including those derived from capacitance,voltage, admittance spectroscopy, deep level transient spectroscopy, time-resolved photoluminescence, Auger emission profiling, Hall effect, and drive level capacitance profiling. Data from each technique were examined for correlation with device performance, and those providing indicators of related properties were compared to determine which techniques and interpretations provide credible values for transport properties. Although these transport properties are not sufficient to predict all aspects of current-voltage characteristics, we have identified specific physical and transport characterization methods that can be combined using a model-based analysis algorithm to provide a quantitative prediction of voltage loss within the absorber. The approach has potential as a tool to optimize and understand device performance irrespective of the specific process used to fabricate the CIGSS absorber layer. Copyright 2005 John Wiley & Sons, Ltd. [source]


    Quadrupolar glass as a model for charge carrier transport in nonpolar organic materials

    ANNALEN DER PHYSIK, Issue 12 2009
    S.V. Novikov
    Abstract Monte Carlo simulation of the charge carrier transport in disordered nonpolar organic materials has been carried out. As a suitable model we considered the model of quadrupolar glass. A general formula for the temperature and field dependence of the mobility was suggested. A comparison with experimental data has been carried out. [source]