Perylene Tetracarboxylic Acid Dianhydride Research Articles

Improved performance of graphite coated by hard carbon of PTCDA sodium salt for lithium-ion batteries

The graphite layers are combined with van der Waals forces. During the charging and discharging process, the graphite layer spacing changes, causing the graphite flakes to peel off and pulverize, resulting in unsatisfactory electrical cycle performance. In addition, lithium ions can only be inserted from the end surface of the graphite, Will inevitably cause the increase of lithium-ion diffusion resistance, and affect the battery rate performance. In this paper, a sodium salt of perylene tetracarboxylic acid dianhydride is used. By adjusting different coating modification processes, the graphite anode particles coated with sodium salt of perylene tetracarboxylic acid dianhydride are further calcined at high temperature to obtain a graphite-like structure The amorphous hard carbon-coated modified graphite anode material, through comparison, it is found that different thicknesses (9–40 nm) of organic carbon coating show different surface morphologies, which effectively improves the structural stability of the graphite anode material. Performance, and finally obtain more excellent capacity, cycle stability performance and rate performance.

Фотофизические свойства тонких пленок перилена, модифицированного функциональными группами диангидрида и диимида тетракарбоновой кислоты

The morphology of organic semiconductor films of perylenetetracarboxylic acid dianhydride (PTCDA) and perylenetetracarboxylic acid dibenzyl-diimide (N, N`-DBPTCDI) formed by thermal vacuum deposition was studied by atomic force microscopy. It was shown that annealing of films at 420 K leads to rearrangement of their structure and crystallization. The optical absorption spectra of the films under study were used to estimate the optical band gap. The temperature dependence of the dark conductivity of PTCDA and N, N-DBPTCDI films before and after annealing (Т = 420 K) was established. The values of the activation energy of charge carrier traps are determined. The computer simulation of the density of localized states in the band gap of the films studied was carried out using the photoconductivity spectra in the constant photocurrent mode. Model photovoltaic cells based on PTCDA / СuPc and N, N-DBPTCDI / СuPc structures were formed. The kinetics of decay of the interfacial photo-voltage of the cells prepared was measured using pulsed light as an excitation source. On the basis of the performed measurements, the charge carrier mobility values in the investigated semiconductor materials were estimated.

Photoluminescence study of the exciton dynamics at PTCDA/noble-metal interfaces

Charge and energy transport across organic/metal interfaces play a decisive role for the functionality of organic semiconductor devices. As well-defined model systems for such heterointerfaces, we consider thin films of the organic semiconductor perylene-tetracarboxylicacid-dianhydride (PTCDA) deposited on the single-crystalline (111)-surfaces of the noble metals silver and gold. By means of time-resolved photoluminescence we investigate the exciton dynamics of these systems in the energy and time domain. Systematic variation of the PTCDA film thickness enables us to follow the exciton relaxation rates as a function of the molecule--metal separation from several nanometers down to a few angstroms. Spatially localized excitations, such as excimers, are found to relax by nonradiative energy transfer to the metal. In contrast, the relaxation of charge-transfer (CT) excitons can be explained by exciton diffusion and subsequent annihilation at the organic/metal interface. Both mechanisms are found to be much more efficient on Ag(111) than on Au(111). For excimers, the faster relaxation on the silver substrate presumably involves the excitation of intraband transitions inside the metal. The higher relaxation rate of CT excitons is explained in terms of enhanced charge transfer across the PTCDA/Ag(111) interface, which is mediated by the electronic interface state inherent to this organic/metal interface.

Multitude of PTCDA Superstructures on Ag(111) and Vicinal Surfaces

Organic molecules that covalently bond to metal surfaces, like perylene tetracarboxylic acid dianhydride (PTCDA) on Ag, may cause large-scale reconstruction of the interface, in particular if the adsorption takes place on a “stepped” (i.e., vicinal) surface. Under certain conditions, such surfaces develop a large variety of high-index facets that are stabilized by superstructures of the PTCDA adsorbate. These superstructures can be commensurate, point-on-line, or incommensurate with respect to the substrate facets depending on facet orientation and step direction. The present scanning tunneling microscopy and low-energy electron diffraction data were taken from two different vicinal surfaces, Ag(775) and Ag(10 8 7), both inclined by 8.5° with respect to the (111) direction but in different azimuthal directions. Altogether, we identify and evaluate 18 new superstructures and correlate their data with the properties of the corresponding facets. The observed richness of superstructures and the occurrence of ...

Electronic properties of the polycrystalline tin dioxide interface with conjugated organic layers

The results on the electronic structure of the unoccupied electronic states of the polycrystalline SnO 2 in the energy range from 5 eV to 25 eV above the Fermi level are presented. The modification of the electronic structure and of the surface potential upon deposition of the ultrathin films of copper phthalocyanine (CuPc) and of perylene tetracarboxylic acid dianhydride (PTCDA) film onto the SnO 2 surface were studied using the very low energy electron diffraction (VLEED) method and the total current spectroscopy (TCS) measurement scheme. A substantial attenuation of the TCS signal coming from the SnO 2 surface was observed upon formation of a 1.5–2 nm thick organic deposit layer while no new spectral features from the deposit were distinguishable. It was observed that the electronic structure typical for the organic films was formed within the organic deposit thickness range from 2 nm to 7 nm. The interfacial charge transfer was characterized by the formation of the polarization layer up to 5 nm thick in the organic films. The PTCDA deposition on SnO 2 was accompanied by the negative charge transfer onto the organic layer and to the 0.65 eV increase the surface work function. At the CuPc/SnO 2 interface, the negative charge was transferred to the SnO 2 surface and the overall surface work function decreased by 0.15 eV.

Preparation of Highly Monodisperse Polymeric Particles Incorporating Polymerizable Perylene-Bisimide Fluorophore

In this work, the yellow emitted perylene-bisimide dye with polymerizable functional groups was synthesized by condensation reaction of perylene tetracarboxylic acid dianhydride and allyl amine. The resulting polymerizable fluorophore was characterized in terms of structure with NMR and FT-IR, the absorption and emission properties by using UV-Vis and fluorescence spectroscopy, respectively. Afterwards, the reactive polymerizable fluorophore was incorporated into the polymer nanoparticle by copolymerization with styrene and acrylic acid monomers via miniemulsion polymerization. The obtained fluorescent nanoparticles was stable and showed a highly monodisperse size distribution with hydrodynamic diameter of 91.8±0.4 nm.

Electronic properties of the surface of perylene tetracarboxylic acid dianhydride film upon deposition of the ultrathin conjugated layers of Pyronine B

Abstract Ultrathin conjugated layers of Pyronine B were thermally deposited in UHV on the surface of perylene tetracarboxylic acid dianhydride (PTCDA) film. The structure of unoccupied electron states located 5–20 eV above the Fermi level ( E F ) and the surface potential were monitored during the Pyronine B overlayer deposition, using an incident beam of low-energy electrons according to the total current electron spectroscopy (TCS) method. Electronic work function of the PTCDA surface changed from 4.9 ± 0.1 eV, during the Pyronine B deposition due to the change of the contents of the surface layer, until it reached a stable value 4.6 ± 0.1 eV at the Pyronine B film thickness 8–10 nm. The interface dipole corresponds to electron transfer from the Pyronine B overlayer to the PTCDA surface and the polarization in the Pyronine B overlayer was found confined within approximately 1 nm near the interfaces. The edges of major bands of density of unoccupied electronic states (DOUS) of PTCDA substrate and of the Pyronine B overlayer were unaffected by the process of the interface formation. The major TCS spectral features of the Pyronine B film corresponding to the DOUS band edges were identified and the assignment of the π * , σ * (C–C) and σ * (C C) character was suggested.

Very high temperature chemical vapor deposition of new carbon thin films using organic semiconductor molecular beam sources

We carried out the preparation and characterization of new carbon films deposited using an organic molecular beam deposition apparatus with very high substrate temperature (from room temperature to 2670 K), which we newly developed. When we irradiated molecular beam of organic semiconductor perylene tetracarboxylic acid dianhydride (PTCDA) on Y 0.07Zr 0.93O 2 (111) at 2170 K, a new carbon material was formed via decomposition and fusing of the molecules. The films were characterized with an atomic force microscope (AFM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Zirconium carbide (ZrC) films were identified beneath the topmost carbon layer by XRD and XPS analyses, which results from chemical reactions of the substrate and the molecules. Partially graphitized aromatic rings of PTCDA were observed from Raman spectroscopy. The present technique – very high temperature chemical vapor deposition using organic semiconductor sources – will be useful to study a vast unexplored field of covalent carbon solids.

Photovoltaic properties of interfaces in organic molecular film-silicon structures

A photovoltaic effect was discovered and studied in the structures comprising thin films of perylenetetracarboxylic acid dianhydride (PTCDA) and oligo(phenylene-vinylene) (OPV) deposited in vacuum onto a silicon surface, as well as in the OPV/PTCDA/Si structure. A change in the surface potential under illumination in the visible spectral range was detected in situ using the electron probe technique. The spectra and the relaxation characteristics of the photoinduced potential were measured. The fast and slow components of the photopotential were revealed, which corresponded to the photoabsorption and relaxation processes in the silicon substrate (fast component) and in the organic film (slow component). These components have opposite signs, which accounts for the photopotential sign change on the passage from the short-wavelength (350–600 nm) to long-wavelength (700–905 nm) spectral regions.

A refined structural analysis of the PTCDA monolayer on the reconstructed Au(1 1 1) surface—“Rigid or distorted carpet?”

The superstructures ( H1 and H2) of perylenetetracarboxylicacid-dianhydride (PTCDA) monolayers on the ( 22 × 3 ) reconstructed Au(1 1 1) surface reported by Mannsfeld et al. [S. Mannsfeld, M. Toerker, T. Schmitz-Hübsch, F. Sellam, T. Fritz, K. Leo, Org. Electron. 2 (2001) 121] are reinvestigated by high resolution low energy electron diffraction (SPALEED). The purpose of this investigation is to elucidate in detail the point-on-line (p-o-l) structural relation of the homogeneous adsorbate layer with respect to the three reconstruction domains of the Au(1 1 1) surface. For the H2 (non-equilibrium) structure, diffraction patterns without a spot splitting are found, indicating an almost perfect undisturbed overgrowth of the domain boundaries of the ( 22 × 3 ) reconstruction. As a consequence, the superstructure does not follow strictly the p-o-l relation, but only in an averaged manner. Contrary for the H1 phase (equilibrium structure), a spot splitting is observed, which indicates that superstructure domains on different Au(1 1 1) reconstruction domains exhibit slightly different angular orientations, thus adopting p-o-l relations on all Au(1 1 1) reconstruction domains. The PTCDA layer on Au(1 1 1) may be thus considered as a rigid or distorted carpet, depending on the preparation conditions.

Interaction Model for the Adsorption of Organic Molecules on the Silver Surface

Adsorption of organics on a silver surface is simulated. An Embedded Atom Model is used for the metal, a standard force field for the organics, and a combination of the charge equilibration model and the Morse potential for their electrostatic and nonbonding interactions. The only adjustable parameters of this approach appear in the Morse potential. They are tuned to reproduce experimental and high level quantum chemical data. The adsorption energies of 13 molecules on the Ag(111) surface are obtained with an average error of less than 1 kcal mol(-1). The model should be transferable to molecules with the same chemical groups used in regressing the potential parameters when physisorption or weak chemisorption, i.e., no bond breaking, occur, and also to other Ag surfaces. When used to simulate perylene tetracarboxylic acid dianhydride (PTCDA) on Ag(111), correct geometry of mono- and multilayers are observed in molecular dynamics simulations at room temperature.

New perylenes for dye sensitization of TiO2

We describe a new generation of perylene photosensitizers based upon N-(2,5-di-tert-butylphenyl)perylene-3,4-dicarboximide. The new sensitizers have more favorable energetics for electron injection into TiO2 and better light absorption properties for solar conversion than previous sensitizers based upon perylene tetracarboxylic acid dianhydride. Syntheses, absorption properties, and electrochemical potentials for the new perylenes are reported. We compare the solar conversion efficiencies of the dyes in the dye sensitized solar cell (DSSC) and discuss trends in terms of energetics and structural differences that may affect the injection and recombination processes. These are the highest efficiencies yet reported for perylene sensitizers in the DSSC.

Electronic polarization at surfaces and thin films of organic molecular crystals: PTCDA

The electronic polarization energies, P= P ++ P −, of a perylenetetracarboxylic acid dianhydride (PTCDA) cation and anion in a crystalline thin film on a metallic substrate are computed and compared with measurements of the PTCDA transport gap on gold and silver. Both experiments and theory show that P is 500 meV larger in a PTCDA monolayer than in 50 Å films. Electronic polarization in systems with surfaces and interfaces are obtained self-consistently in terms of charge redistribution within molecules.

Charge redistribution and polarization energy of organic molecular crystals

We present an approach to electronic polarization in molecular solids treated as a set of quantum systems interacting classically. Individual molecules are dealt with rigorously as quantum-mechanical systems subject to classical external fields created by all other molecules and, possibly, external sources. Self-consistent equations are derived for induced dipoles and for atomic charges whose redistribution in external fields is given explicitly by an atom-atom polarizability tensor. Electronic polarization is studied in two representative organic molecular crystals, anthracene and perylenetetracarboxylic acid dianhydride (PTCDA), and contrasted to previous results for systems of polarizable points. The stabilization energies of the neutral lattice, of isolated anions and cations, and of cation-anion pairs are found. Charge redistribution on ions is included. The dielectric tensors of crystals are successfully related to gas-phase properties and provide consistency checks on polarization energies. The procedure is generally applicable to organic crystals in the limit of no intermolecular overlap.

Charge redistribution and electronic polarization in organic molecular crystals

The electronic polarization of organic molecular crystals is obtained using the atom–atom polarizability tensor and charge redistribution in addition to previous theory based on induced dipoles. The dielectric tensors of anthracene and perylenetetracarboxylic acid dianhydride (PTCDA) crystals are successfully related to molecular polarizabilities.

Vibronic structure of PTCDA stacks: the exciton–phonon-charge-transfer dimer

Perylenetetracarboxylic acid dianhydride (PTCDA) stacks face-to-face in crystals and multiple quantum wells (MQWs). Excitations of PTCDA stacks are mixed molecular (Frenkel) and charge-transfer (CT) states coupled to a molecular vibration. Eclipsed stacks and molecular conjugation imply strong Frenkel–CT mixing in absorption and electroabsorption, with k=0 at the top of the exciton band, and negligible mixing at k=π for emission from the bottom. The exciton–phonon-CT dimer developed for k=0 processes is a nonadiabatic approximation for narrow CT bands. Quantitative dimer spectra are obtained in the vibronic basis of displaced harmonic oscillators for excited PTCDA and radical ions. We present a joint analysis of absorption and emission in PTCDA stacks and MQWs using parameters from solution, molecular calculations, and related conjugated systems. Polarized single-crystal absorption decisively relates the entire 2–3 eV system to molecular π–π* transitions, while electroabsorption with field along the stack implicates adjacent ions in the stack. The simple structure and extensive PTCDA spectra make possible detailed modelling of mixed Frenkel–CT vibronics that were far less accessible in previous organic molecular crystals. Since the coupled mode is closely related to polyenes and conjugated polymers, PTCDA provides a bridge between molecular insulators and extended systems capable of charge transport.

Adsorption site determination of PTCDA on Ag(110) by manipulation of adatoms

Simultaneous imaging of organic molecules and an underlying metallic substrate lattice is often hampered by tip-induced molecular motion, even at low temperatures. In the case of perylene-tetracarboxylic acid-dianhydride (PTCDA) on Ag(110), this problem is circumvented by using tip-induced motion of a coadsorbed Ag atom to obtain convenient markers of the substrate lattice. A model for the registry of PTCDA on Ag(110) is deduced.

Efficiency of Modified Phthalocyanine Compounds as Antioxidants and UV Stabilizers for SBR Vulcanizates

Modified phthalocyanine compounds were prepared from the condensation of 3, 4, 9, 10 perylene tetracarboxylic acid dianhydride, phthalic anhydride and urea with and without chloride salts of Fe II, Co II, and Ni II, under phthalocyanine preparation conditions by the urea fusion technique. The highly coloured metal free-, Fe-, Co-, and Ni-modified phthalocyanine compounds were incorporated into styrene-butadiene rubber (SBR) mixes. The rheometric characteristics of the rubber mixes were determined. The physico-mechanical properties of SBR vulcanizates were evaluated with and without exposure to thermal ageing. The obtained results revealed that Ni-modified phthalocyanine has superior efficiency as an antioxidant for SBR vulcanizates, and 1 phr of that compound is the optimum concentration. UV exposed SBR vulcanizates showed that nickel-modified phthalocyanine is a good UV stabilizer and 2 phr is the optimum concentration that can be significantly used in SBR. All samples subjected to UV radiation showed no significant change of colour up to 300 hrs of exposure.