One-dimensional Organic Semiconductors Research Articles

Design of one-dimensional organic semiconductors with high intrinsic electron mobilities: lessons from computation

A bottom-up design strategy for one-dimensional organic semiconductors with high intrinsic electron mobilities is proposed.

Topochemical Polymerization of a Nematic Tetraazaporphyrin Derivative To Generate Soluble Polydiacetylene Nanowires.

Polydiacetylenes are well-established one-dimensional organic semiconductors that have been generated by photochemical and thermal polymerizations of diacetylenes in single crystals, gel phases, thin films, and membranes. Their formation in mesophases, such as liquid crystals, has been surprisingly little studied although higher-ordered mesophases should support the topochemical polymerization of diacetylenes (1,3-butadiyne groups) and may give access to large domains of uniformly aligned materials. The polymerization of diacetylenes in a mesophase may also increase the stability of the self-assembled supramolecular structure. Here, the dye and discotic mesogen tetraazaporphyrin was decorated with eight diacetylene-containing alkyl chains to probe its mesomorphism and conversion into multifunctional polydiacetylene materials. While the incorporation of diacetylene groups supports columnar mesomorphism, successful photopolymerization required the presence of directing amide groups that suppressed columnar in favor of nematic mesomorphism. Still, the polymerization of the nematic mesophase generated a soluble nematic polydiacetylene of significantly higher molecular weight (Mn = 77 kDa or 25 monomer units by gel permeation chromatography) than what has been obtained in gel phases of related compounds. The formation of polydiacetylene was confirmed by Raman spectroscopy, and its nematic structure was verified by UV-vis spectroscopy, polarized optical microscopy, and X-ray diffraction. Both its nematic structure and the incorporation of eight side chains per discotic unit provide the polydiacetylene with sufficient solubility for casting thin films on substrates. Atomic force microscopy studies of films on silicon wafers revealed a grid-like structure of connected nanofibers. This study demonstrates the requirements for the formation of multifunctional mesomorphic polydiacetylene materials from mesomorphic precursors and their advantages. Optimization of the presented molecular design should give access to other mesophases and, consequently, functional polydiacetylene materials with tunable structures and optoelectronic properties.

Molecular Engineering of Mesomorphic Fluorene-Bridged Triphenylene Triads: Thermotropic Nematic/Columnar Mesophases, and p-Type Semiconducting Behavior

Discotic polyaromatic liquid crystals exhibiting 2D columnar mesophases are actively investigated for their potential utilization as one-dimensional organic semiconductors, due essentially to their long-range order self-organization and high charge carrier transport ability. The much less reported nematic-containing discotic materials have however been recently found to be of industrial importance too. In this context, highly conjugated fluorene-bridged triphenylene triads have been designed with the aim of inducing room temperature nematic phases. In our approach, the length of the alkyl chains bore by the central fluorene unit was changed in order to constrain the space-filling, to modulate the intermolecular π–π interactions, and to control the tendency of the molecular triads to stack into columns, and the subsequent aggregation of the columns in specific ways. This strategy was successful, and in addition to the naturally expected two-dimensional columnar mesophases, most triads exhibit the more elus...

Phase behaviors of binary mixtures composed of electron-rich and electron-poor triphenylene discotic liquid crystals**Project supported by the National Natural Science Foundation of China (Grant Nos. 51273133 and 51443004).

Disk-like liquid crystals (DLCs) can self-assemble to ordered columnar mesophases and are intriguing one-dimensional organic semiconductors with high charge carrier mobility. To improve their applicable property of mesomorphic temperature ranges, we exploit the binary mixtures of electronic donor-acceptor DLC materials. The electron-rich 2,3,6,7,10,11-hexakis(alkoxy)triphenylenes (C4, C6, C8, C10, C12) and an electron-deficient tetrapentyl triphenylene-2,3,6,10-tetracarboxylate have been prepared and their binary mixtures have been investigated. The mesomorphism of the 1:1 (molar ratio) mixtures has been characterized by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and small angel x-ray scattering (SAXS). The self-assembled monolayer structure of a discogen on a solid-liquid interface has been imaged by the high resolution scanning tunneling microscopy (STM). The match of peripheral chain length has important influence on the mesomorphism of the binary mixtures.

Tunable Band Alignment with Unperturbed Carrier Mobility of On-Surface Synthesized Organic Semiconducting Wires.

The tunable properties of molecular materials place them among the favorites for a variety of future generation devices. In addition, to maintain the current trend of miniaturization of those devices, a departure from the present top-down production methods may soon be required and self-assembly appears among the most promising alternatives. On-surface synthesis unites the promises of molecular materials and of self-assembly, with the sturdiness of covalently bonded structures: an ideal scenario for future applications. Following this idea, we report the synthesis of functional extended nanowires by self-assembly. In particular, the products correspond to one-dimensional organic semiconductors. The uniaxial alignment provided by our substrate templates allows us to access with exquisite detail their electronic properties, including the full valence band dispersion, by combining local probes with spatial averaging techniques. We show how, by selectively doping the molecular precursors, the product’s energy level alignment can be tuned without compromising the charge carrier’s mobility.

ChemInform Abstract: Synthesis of Columnar Liquid Crystals

AbstractReview: 213 refs.

Research on Charge Transport in One-Dimensional Organic Semiconductors Material

1D conjugated polymers belong to the family of organic semiconductor materials, in which the charge carriers are polarons or bipolarons. Charge transport in 1D organic semiconductors in the presence of high electric fields is studied within the SSH model. It is found that under a sufficiently high electric field, the polaron is dissociated into free-like electron. The electron performs Bloch oscillation (BO) in the organic semiconductors. By enhancing the electric field, BO will be destroyed and electrons can transit from the valence band to the conduction band, which is Zener tunneling in organic semiconductors. The results also indicate a field-induced insulator-metal transition.

Erratum: “Transition from dynamic to static disorder in one-dimensional organic semiconductors” [J. Chem. Phys. 131, 014703 (2009)

First Page

Zener Tunneling in One-Dimensional Organic Semiconductors at Finite Temperature

Zener tunneling at finite temperature in one-dimensional organic semiconductors under an external electric field is studied within the framework of a tight-binding model. The temperature effect is simulated by the introduction of random forces to lattice motion. It is found that the critical field strength of Zener tunneling decreases with the increasing temperature. Under sufficiently high electric field, dielectric breakdown occurs, which is characterized by the irreversibility of the energy gap.

Transition from dynamic to static disorder in one-dimensional organic semiconductors

A generic model Hamiltonian is proposed for the study of the transport in a quasi-one-dimensional semiconductor in the charge transport regime intermediate between dynamic localization and static localization due to structural disorder. This intermediate regime may be appropriate for many organic semiconductors, including polymers, discotic liquid crystals, and DNA. The dynamics of the charge carrier is coupled to classical Langevin oscillators whose spectral density can be adjusted to model experimental systems of interest. In the proposed model, the density of states is constant (at constant temperature) and the transition from dynamic to static disorder is controlled by a single parameter. This paper further clarifies that the density of states may not contain all the information needed to describe the charge transport in some materials.

Zener tunneling in one-dimensional organic semiconductors

Tunneling effect in one-dimensional organic semiconductors in the presence of an external electric field is studied within the framework of a tight-binding model and a nonadiabatic dynamical method. It is found that under a high electric field, electrons can transit from the valence band (VB) to the conduction band (CB), which is demonstrated to be Zener tunneling in organic semiconductors. The results also indicate a field-induced insulator–metal transition accompanied by the vanishing of the energy gap. It is found that, after the field is turned off, the Peierls phase cannot be recovered.

Excitonic effects in a time-dependent density functional theory

Excited state properties of one-dimensional molecular materials are dominated by many-body interactions resulting in strongly bound confined excitons. These effects cannot be neglected or treated as a small perturbation and should be appropriately accounted for by electronic structure methodologies. We use adiabatic time-dependent density functional theory to investigate the electronic structure of one-dimensional organic semiconductors, conjugated polymers. Various commonly used functionals are applied to calculate the lowest singlet and triplet state energies and oscillator strengths of the poly(phenylenevinylene) and ladder-type (poly)(para-phenylene) oligomers. Local density approximations and gradient-corrected functionals cannot describe bound excitonic states due to lack of an effective attractive Coulomb interaction between photoexcited electrons and holes. In contrast, hybrid density functionals, which include long-range nonlocal and nonadiabatic corrections in a form of a fraction of Hartree-Fock exchange, are able to reproduce the excitonic effects. The resulting finite exciton sizes are strongly dependent on the amount of the orbital exchange included in the functional.

Perylenediimide Nanowires and Their Use in Fabricating Field-Effect Transistors and Complementary Inverters

Perylenetetracarboxyldiimide (PTCDI) nanowires self-assembled from commercially available materials are demonstrated as the n-channel semiconductor in organic field-effect transistors (OFETs) and as a building block in high-performance complementary inverters. Devices based on a network of PTCDI nanowires have electron mobilities and current on/off ratios on the order of 10(-2) cm2/Vs and 10(4), respectively. Complementary inverters based on n-channel PTCDI nanowire transistors and p-channel hexathiapentacene (HTP) nanowire OFETs achieved gains as high as 8. These results demonstrate the first example of the use of one-dimensional organic semiconductors in complementary inverters.

Origin and stabilization of photoexcitations in conjugated polymers

We report studies on the nature of photoexcitations in onedimensional organic semiconductors using photoluminescence, absorption and photoinduced absorption techniques. The polymers of interest —ladder-type poly( para-phenylenes) (LPPPs) —show high intrachain order and a small distribution of effective conjugation lengths, which makes them a perfect model system for conjugated polymers. The influence of the effective conjugation length on the energetic position and the stabilization of photoexcited charged and neutral states is investigated. Interchain interactions are discussed on the base of optical spectroscopy under hydrostatic pressure.

Conductivity Spectrum Fine Structure of One‐Dimensional Organic Semiconductors

physica status solidi (b)Volume 100, Issue 1 p. K97-K100 Short Note Conductivity Spectrum Fine Structure of One-Dimensional Organic Semiconductors V. M. Yartsev, V. M. Yartsev Danmarks Tekniske Hojskole, Copenhagen Permanent address: Kuibyshev State University, ul. Akad. Pavlova 1, 443086 Kuibyshev, USSR.Search for more papers by this authorM. J. Rice, M. J. Rice Xerox Webster Research Center, Webster and NORDITA, CopenhagenSearch for more papers by this author V. M. Yartsev, V. M. Yartsev Danmarks Tekniske Hojskole, Copenhagen Permanent address: Kuibyshev State University, ul. Akad. Pavlova 1, 443086 Kuibyshev, USSR.Search for more papers by this authorM. J. Rice, M. J. Rice Xerox Webster Research Center, Webster and NORDITA, CopenhagenSearch for more papers by this author First published: 1 July 1980 https://doi.org/10.1002/pssb.2221000162Citations: 7 Copenhagen, DK 2800, Denmark. Webster, New York 14580, USA. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume100, Issue11 July 1980Pages K97-K100 RelatedInformation