Electronic Properties Of Poly Research Articles

Electronic Properties of Poly(N-vinylcarbazole) Using semi-empirical oligomer extrapolation approximations

Poly(N-vinylcarbazole) has been widely used in polymer light emitting diodes due to its unique electronic properties. The electronic properties of Poly(N-vinylcarbazole) were examined using the Semi-Empirical Zerner Modified Intermediate Neglect of Differential Overlap (ZINDO) oligomer extrapolation method. In this calculation, the electronic properties of Poly(N-vinylcarbazole) were extracted from oligomer electronic properties. We identified a tendency for oligomers with large HOMO-LUMO gaps in the form of linear regression as function of reciporocal of monomeric units. The increasing number of monomers induce the interaction between energy levels of each monomer which boardening the energy levels. The localized molecular orbital and vibration spectra of the basic unit of polymer Poly(N-vinylcarbazole) also has been investigated.

Solvent Impact on Langmuir and Langmuir–Schaefer Films of Soluble Main‐Chain Poly(fullerene)s Based on C60

Understanding the morphology and electronic properties of poly(fullerene)s is crucial for the development of new organic devices. This work addresses the fabrication and characterization of Langmuir–Schaefer (LS) films of poly(fullerene)s based on C60 with short (HSS8) and long (HSS16) sidechains, solubilized in chloroform or xylene. In addition, density functional theory (DFT) calculations are used to optimize the molecular geometries, determine energies, and investigate the influence of solvent applied. Depending on the organic solvent, floating material isotherms indicate the formation of disordered aggregates in the aqueous subphase. The influence of solvent in LS films is also evidenced by way of atomic force microscopy (AFM), UV‐vis, and cyclic voltammetry (CV) measurements. From DFT calculations, the arms of the poly(fullerene)s start to extend from an initial position of surrounding the fullerene sphere. In AFM measurements, depending on the organic solvent, the roughness significantly reduces, while the homogeneity is much higher. In UV‐vis and CV measurements, the propensity to form aggregates depends mainly on the polarization of the solvent and is directly related to the maximum absorption, oxidation, and reduction peaks. From the optical bandgap energy values, the poly(fullerene)s studied here present high potential for application in organic electronic devices.

On the non-bonding valence band and the electronic properties of poly(triazine imide), a graphitic carbon nitride.

Graphitic carbon nitrides are covalently-bonded, layered, and crystalline semiconductors with high thermal and oxidative stability. These properties make graphitic carbon nitrides potentially useful in overcoming the limitations of 0D molecular and 1D polymer semiconductors. In this contribution, we study structural, vibrational, electronic and transport properties of nano-crystals of poly(triazine-imide) (PTI) derivatives with intercalated Li- and Br-ions and without intercalates. Intercalation-free poly(triazine-imide) (PTI-IF) is corrugated or AB stacked and partially exfoliated. We find that the lowest energy electronic transition in PTI is forbidden due to a non-bonding uppermost valence band and that its electroluminescence from the π-π* transition is quenched which severely limits their use as emission layer in electroluminescent devices. THz conductivity in nano-crystalline PTI is up to eight orders of magnitude higher than the macroscopic conductivity of PTI films. We find that the charge carrier density of PTI nano-crystals is among the highest of all known intrinsic semiconductors, however, macroscopic charge transport in films of PTI is limited by disorder at crystal-crystal interfaces. Future device applications of PTI will benefit most from single crystal devices that make use of electron transport in the lowest, π-like conduction band.

Study of the Effect of Solvent on the Conductivity of Langmuir-Schaefer Films of Poly(Fullerene)s

The present work aims to prepare and characterize very thin films of poly(fullerene)s in order to investigate their electrical properties and the influence of xylene and chloroform solvents on these materials. The fullerenes studied were phenyl-C61-butyric acid methyl ester (PCBM), oligo{(phenyl-C61-butyric acid methyl ester)-alt-[1,4-bis(bromomethyl)-2,5-bis(octyloxy)benzene]} (OPCBMMB) and poly{[bispyrrolidino(phenyl-C61-butyric acid methyl ester)]-alt-[2,5-bis(octyloxy) benzene]} (PPCBMB), along with poly(3-hexylthiophene) (P3HT). The Langmuir-Schaeffer technique was used to prepare films, which were deposited on interdigitated gold substrates, and electrically characterized, with emphasis on the study of transport, conductivity and mobility mechanisms with respect to the solvents used. We found that the addition of P3HT significantly increased the conductivity of these materials. The xylene cast PPCBM, in both pure and mixed forms under dark conditions, presented the best conductivity results with respect to the other materials. However, when chloroform was used, it was found that OPCBMMB in both pure and mixed forms under light, exhibited the best conductivities. This is the first treatment, to our knowledge, of the impact of solvents on the electronic properties of poly(fullerene)s.

Consequences of gamma-ray irradiation on structural and electronic properties of PEDOT:PSS polymer in air and vacuum environments.

In this work, the effects of gamma-ray irradiation (up to 3 kGy) on the structural and electronic properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), irradiated in air and vacuum environments are systematically investigated. Raman spectroscopy indicates that there is no significant change in structural conformation of PEDOT:PSS film after gamma-ray irradiation. However, the conductivity of the film decreases as a function of dose in both air and vacuum environments, which can be deduced as a result of defects created in the structure. Hall effect measurements showed higher carrier concentration when the samples are irradiated under vacuum in comparison to the air environment, whereas mobility decreases as a function of dose irrespective of the environment. Furthermore, the electron spin resonance spectra provided evidence of the evolution of polaron population after gamma-ray exposure of 3 kGy, due to the decrease in charge delocalization and molecular ordering of the molecules. This decrease in conductivity and mobility of the PEDOT:PSS films irradiated in air and vacuum environments can be mainly ascribed to the defects and radical formation after gamma-ray exposure, favoring chain scission or cross-linking of the polymers.

A theoretical study of the structural and electronic properties of poly(9-vinylcarbazole) interacting with small-diameter single-walled carbon nanotubes

Density functional perturbation theory (DFPT) and time-dependent density functional perturbation theory (TDDFPT) calculations were employed to study the molecular and electronic structures, linear and nonlinear optical properties, optical phonon modes and vibrational properties of the interaction of poly(9-vinylcarbazole) (PVK)–small-diameter single-walled carbon nanotube (SWCNT) composites. Our calculations show that the chemical connection between PVK and SWCNTs is only through the relatively weak [Formula: see text]–[Formula: see text] and [Formula: see text]–H bonds. PVK and SWCNTs have different electron accepting abilities and we believe this is the major factor responsible for the charge transfer processes we observe in the calculations. We notice an increase in polarizability value from 152 a.u. (PVK) to 517 a.u. (PVK–SWCNTs), making the PVK–SWCNT composite an ideal model for applications such as mechanical and optoelectronics. Also, the result of our calculations under the time-dependent density functional perturbation theory hinges on the idea that the large value of the polarizability calculated for our composite model is an attribute which can be inferred to processes of charge transfer. Our finding corroborates the fact that non-covalent functionalization is one of the effective chemical methods by which the nonlinear optical response properties of PVK–SWCNT composite may be enhanced.

An investigation on the effect of the monomer/catalyst ratio in the electronic properties of poly(3-hexylthiophene) using XPS, REELS and UPS techniques

We report the characterization of poly(3-hexylthiophene) (P3HT) synthesized with different monomer/catalyst ratios. It was shown that changing this parameter in the synthesis of the polymer affects their characteristics such as absorption spectrum and energy levels. We also compared different techniques to determine the polymer band gap. Most importantly, we showed that optoelectronic properties, particularly those obtained by reflection electron energy loss spectroscopy (REELS technique), can be used to obtain the electronic band gap when cyclic voltammetry does not detect the reduction potential. Power conversion efficiencies of 1.2 and 2.3% were obtained for P3HT (sample with higher molar mass) in conventional and inverted configuration.

Control over chiroptical and electronic properties of poly(9,9′-bifluorenylidene) bearing chiral side chains

The introduction of chiral side chains at peripheral positions of the 9,9′-bifluorenylidene moiety causes an efficient bias to its dynamic molecular helicity, which helps control the chiroptical and electronic properties of resultant polymers.

Boron‐Centered Scorpionate‐Type NHC‐Based Ligands and Their Metal Complexes

The success enjoyed in the last 50 years by use of poly(pyrazolyl)borates as ligands has inspired the development of a great number of scorpionates containing other donor elements. These include polytopic bis‐ and tris(NHC)borate ligands, featuring N‐heterocyclic carbene (NHC) moieties that generally coordinate as bidentate κ2C or tridentate κ3C, respectively. In spite of structural similarities between poly(pyrazolyl)borates and poly(NHC)borates, their methods of synthesis and their reactivity are different and reflect the variations in topology, flexibility, and donor properties. The structural and electronic properties of poly(NHC)borate ligands are compared and correlated with their coordination chemistry, particularly towards transition metals. The advances in the chemistry of scorpionate‐type bis‐ and tris(NHC)borate ligands are reviewed by highlighting and comparing their structural properties and their ability to stabilize low to high metal oxidation states in transition‐metal complexes.

Multichromic polymers based on pyrene clicked thienylpyrrole

In this study, the effect of pendant pyrene on the optical and electronic properties of poly(2,5-dithienylpyrrole)s was studied. For this purpose a new pyrene coupled 2,5-dithienylpyrrole derivative (SNS-pyrene) was synthesized through click reaction. SNS-pyrene was electrochemically polymerized and its electrochemical and optical properties were investigated by electrochemical and optical techniques. The polymer had a band gap of 3.36 eV and displayed light green to blue color variation upon oxidation in less than 2.48 s. Additionally, electrochemical copolymerization of SNS-pyrene with 3,4-ethylenedioxythiophene was achieved whilst a detailed investigation was performed on the effect of electrochemical polymerization conditions on the optoelectronic properties of the copolymers. Studies revealed that the copolymers exhibit multichromic reversible redox behavior with lower band gaps and shorter switching times than their parent polymer, P(SNS-pyrene) © 2014 Society of Chemical Industry.

Tuning optical and electronic properties of poly(4,4'-triphenylamine vinylene)s by post-modification reactions

New triphenylamine-based polyarylenevinylenes with pendant phenylethynyl- and 3-pyridylethynyl substituents were synthesized by Stille polycondensation of trans-1,2-bis(tributylstannyl)ethene with two new ethynyl substituted triphenylamine monomers, i.e., N,N-bis(4-iodophenyl)-4'-(phenylethynyl) phenylamine and N,N-bis(4-iodophenyl)-4'-(3-pyridylethynyl) phenylamine. The polymers were characterized by spectral methods and cyclic voltammetry and their properties were compared with those of the unsubstituted poly(4,4'-triphenylamine vinylene). Chemical post-modifications of the polymers by tetracyanoethylene addition to the triple bond, and quaternization of pyridyl group with accent on the fine-tuning of the optical and electrochemical properties were also studied. Density functional theory calculations provide a reliable interpretation of the observed spectra and electrochemical data.

Structure and electronic properties of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) prepared under ultrasonic irradiation

Poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) anions (PEDOT/PSS) is widely used in efficient organic optoelectronic devices. The main drawback of the commercially available PEDOT/PSS aqueous dispersions is their instability. In the present work stable aqueous dispersion of PEDOT/PSSus with predominant size of polymer nanoparticles about 20nm is prepared by oxidative polymerization of 3,4-ethylenedioxythiophene under sonication. Sonication greatly accelerates preparation as well as increases crystallinity and conductivity of PEDOT/PSSus in comparison with the samples prepared by the common route without the application of ultrasound. It is shown that the use of diethylene glycol, dimethylformamide or dimethylsulfoxide as secondary dopants of PEDOT/PSSus increases the conductivity of the polymer films in more than one order and simultaneously decreases the value of electron work function that is important for optoelectronic applications of the polymer.

Enhanced electroluminescence of organic light-emitting diodes by using halloysite nanotubes

The effect of halloysite clay nanotubes (HNTs) on the optical and electronic properties of poly(2-methoxy-5-[2′-ethylhexyloxy]-1,4-phenylenevinylene) (MEH-PPV) have been investigated. The UV–vis absorption band of the conjugated polymer remains unchanged upon the incorporation of halloysite nanotubes (HNTs). Photoluminescence (PL) measurements reveal a decreased quantum yield in the MEH-PPV/HNTs nanocomposites, compared with bulk MEH-PPV. Improvement of the electroluminescence of organic light-emitting diodes (OLEDs) was achieved by incorporating high contents of HNTs. The nanotubes act to enhanced polymer aggregates, as revealed by AFM analysis, thus increasing charge transport and therefore electroluminescence but also decreasing PL quantum yield.

Effect of Surface Chemisorption between Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) and Ag Nanoparticles on the Conductivity of the Nanocomposite Film

Abstract The effects of Ag nanoparticle (NP) incorporation on the bonding state and electronic properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films were investigated. Surface stabilization of the Ag NPs by trisodium citrate effectively prevented aggregation of the Ag NPs. The introduction of Ag NPs induced PEDOT moieties as chemisorption centers. The resulting PEDOT-rich film surface with Ag NPs was responsible for the enhanced film conductivity and decreased work function of the Ag NP–PEDOT:PSS film.

Electronic Properties of Poly[3-(1,1-dimethylpropyl)thiophene] and Poly(3-cyclohexylthiophene)

Abstract Poly(3-alkylthiophene) (P3AT) with alkyl side chains longer than or equal to butyl is soluble in some solvents and fusible. However, conductive states of P3AT are unstable. In order to develop soluble conductive polymers with a stable conductive state, electronic properties of poly[3-(1,1-dimethylpropyl)thiophene] (P3DMPT) and poly(3-cyclohexylthiophene) (P3cHT) were compared with those of poly(3-octylthiophene) (P3OT). The photoabsorption spectrum of P3DMPT did not change before and after doping with NOBF4. This is due to its high oxidation potential. The oxidation peak in the cyclic voltammogram of P3DMPT was 1.65 V vs. Ag/Ag+, which is too high to be doped with NOBF4. Polaron peaks were observed after the doping of P3cHT. The polarons of P3cHT decayed faster than those of P3OT with time. However, the behavior of the electron spin resonance spectrum of P3cHT was different from that of P3OT: the spin concentration of P3cHT decreased, whereas the spin concentration of P3OT increased with time. The conductive state of P3cHT will decay through different mechanism of P3OT: their dedoping will be a reverse process of doping. The reverse dedoping processes of P3cHT will be due to the high oxidation potentials of P3cHT.

Visualizations of charge transfer for the model of poly(3,4-alkylenedioxythiophene)s in neutral and various oxidation states

The charge transfer mechanisms of the poly(3,4-alkylenedioxythiophene)s model in neutral and various oxidation states are theoretically investigated, which is stimulated by the recent experimental reports [C. Lin, et al., J. Am. Chem. Soc. 2011, 133, 11339.]. Due to the difference of charge distribution on different units at various oxidation states, the bond lengths of inter-units are significantly different. The properties of excitons and polarons in poly(3,4-alkylenedioxythiophene)s model in neutral and various oxidation states were revealed by quantum chemical calculations. In particular, simultaneous use of different correlation plots in atomic site representation and transition densities in real space representation reveals the electronic structure and spatial localization of the elementary excitations. Theoretical results state that the charge transfer mechanisms for neutral and oxidation states are significantly different. The theoretical results promote deeper understanding for the structural, optical and electronic properties of poly(3,4-alkylenedioxythiophene)s model, and will offer crucial hints for the rational design of novel transparent conductive poly(3,4-alkylenedioxythiophene)s and relative polymers.

Effects of Surface Modification on The Adsorption Behavior and Electronic Properties of Poly(3-hexylthiophene) Adlayer Self-Assembled onto Au(111) Surfaces

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Structural and Electronic Properties of Poly[N-(2-cyanoalkyl)pyrrole]s Bearing Small Alkyl Groups

The electronic and structural properties of poly[N-(2-cyanoalkyl)pyrrole]s bearing short alkyl groups have been investigated using different methodologies. Specifically, the electronic properties of poly[N-(2-cyanoethyl)pyrrole], which was prepared by anodic polymerization, have been determined using both electrochemical and spectroscopic techniques. On the other hand, quantum mechanical calculations on model oligomers of poly[N-(2-cyanomethyl)pyrrole] have been used to propose the conformation of an idealized polymer chain and to examine the influence of the conformation on the predicted electronic properties. Results indicated that the electronic properties of poly[N-(2-cyanoalkyl)pyrrole]s are not only influenced by effect of the conformation in the conjugation of the π-system but also by the existence of secondary oxidative processes on the pyrrole ring of selected repeating units. In this case, the combination of experimental information and quantum mechanical calculations proved to be essential to propose a structural model. This consists of a cross-linked structure formed by small branches of around nine repeating units in each one, with a carbonyl group at the last repeating unit of each branch.

Electronic properties of poly(thiophene-3-methyl acetate)

The electronic structure of poly(thiophene-3-methyl acetate) has been investigated using UV–vis absorption spectroscopy and quantum mechanical calculations. Experimental measures in chloroform solution indicate that the π-conjugation length increases with the polymer concentration, which is reflected by the red shift of the absorbance peak of the π-π* transition. On the other hand, the energy required for the π-π* transition has been found to decrease with the volatility of the solvent for concentrated polymer solutions, even though the influence of the solvent is very small for dilute solutions. Quantum mechanical calculations indicate that the interactions between the π-conjugated backbone and the methyl acetate side groups are very weak. On the other hand, the lowest energy transition predicted for an infinite polymer chain that adopts the anti-gauche and all-anti conformations is 2.8 and 1.9 eV, respectively. Finally, measurements on spin-casted nanofilms reflect that the π-π* transition energy increases with the thickness, which has been attributed to the distortion of the molecular conformation. In spite of this, the energy gap obtained for the thinnest film (1.52 eV) is significantly smaller than that determined for dilute and concentrated chloroform solutions (2.56 and 2.09 eV, respectively). The π-conjugation length and the energy required for the π-π* transition of poly(thiophene-3-methyl acetate) have been examined in different environments (i.e. gas-phase, dilute and concentrated solutions considering solvents with different polarity and volatility, and spin-casted nanofilms) using a combination of UV-vis spectroscopy and quantum mechanical calculations.

From Poly(3,4-ethylenedioxythiophene) to Poly(3,4-phenylenedioxythiophene): Impact of the Substitution of the Ethylene Bridge by the Phenyl Ring on the Molecular Properties

The structural and electronic properties of poly(3,4-phenylenedioxythiophene) and poly(3,4-ethylenedioxythiophene) have been studied using quantum mechanical methods. Calculations have been performed considering a series of oligomers up to 12 repeating units in the neutral and cation states, results being used to extrapolate the properties of the two polymers in the undoped and doped states. Moreover, the electronic properties were estimated in the gas phase and acetonitrile solution, the latter solvent being used in the electrogeneration of the two conducting polymers. A detailed analysis of the results indicates that, although the pi-pi* transition energy of poly(3,4-ethylenedioxythiophene) is lower than that of poly(3,4-phenylenedioxythiophene) in the neutral state, the latter behaves as excellent electronic conductor upon p-doping. Accordingly, the oxidized poly(3,4-phenylenedioxythiophene) shows the lowest pi-pi* electron transition energy.