X.M. Pan

Calculated UV-Visible spectra and third-order nonlinear optical properties of heteroaromatic derivatives of stilbene inserted with 1,3-squaraine

Based on the geometry optimized by semi-empirical PM3 method, UV-visible spectra and second-order hyperpolarizability γ of the heteroaromatic derivatives of stilbene inserted with 1,3-squaraine were calculated by ZINDO/CI-SOS method. The relation between y and molecular structures was discussed. It is shown that the heteroaromatic derivatives of stilbene inserted with 1.3-squaraine will be promising candidates for nonlinear optical materials. which have both larger γ values and high transparency.

Theoretical study on the electronic structure and optical properties of carbazole-π-dimesitylborane as bipolar fluorophores for nondoped blue OLEDs

Molecules with D-π-A structures are drawing increased attention for applications in organic electronic devices due to their distinct optoelectronic properties. A study of a new series of bipolar fluorophores that have been chemically modified for use as highly efficient nondoped blue organic light-emitting diodes (OLEDs) has been carried out based on existing molecular structures and a literature survey. The aim of this study is to provide a profound interpretation of the optical and electronic properties and the structure-property relationships of a series of new bipolar fluorophores. The study also aims to predict the photophysical and optoelectronic properties of the new fluorophores. The density functional theory (DFT) has been confirmed as reliable, especially in predicting the properties of unknown products. The geometry and the electronic structure of these molecules in the ground state were studied with DFT and ab initio HF, whereas the lowest singlet excited-state geometries were optimized by ab initio singlet configuration interaction (CIS). The absorption and emission spectra, both in the gas phase and in THF, and the lowest singlet excited energies were calculated by employing the time-dependent density functional theory (TDDFT) and the polarizable continuum model (PCM). To precisely predict the charge-transporting and charge-confining properties of the new fluorophores, three-layered devices have been simulated. The results show that the molecular geometries, HOMOs, LUMOs, energy gaps, ionization potentials (IP), electron affinities (EA), radiative lifetimes (τ), absorption and emission spectra are all tuned by chemical modifications with different π-conjugated bridges. The results also show that these molecular materials could be used as bipolar light-emitting materials for blue and deep-blue OLEDs.

Theoretical study on C60-doped polyacenic semiconductor(PAS) interacting with lithium

The characteristics of Li n n+C 60 endohedral and exohedral complexes (n=1,2,3,4) in C 60 -doped polyacenic semiconductor (PAS) have been investigated by semiempirical MO AMI calculations with the confirmation made using density functional theory. According to the binding energy, lithium ions are inclined to stay outside of the carbon cage. It is most possible for only single lithium ion to enter C 60 . Moreover, the structure of C 60 is little changed by lithium ions. Basing on these theory results, we explain the reason why the charge/discharge capacity is decreased while the cycle times are increased when C 60 -doped PAS is used as the cathode material for Li-ion battery.

The modulation of electronic and optical properties of OXD-X through introduction of the electron-withdrawing groups: a DFT study.

A comparative study using density functional theory (DFT) on the molecular structure, electronic structure and relative properties of 1,3,4-oxadiazole dimers 1,3-bis[2-(4-methylphenyl)-1,3,4-oxadiazol-5-yl]benzene (OXD-X) and its derivatives with alkoxy substituents -O(CH(2))(n-1)CH(3) (OXD-An, n=1, 2) and electron-withdrawing substituents -CN (OXD-C), -CF(3) (OXD-TFM), -NO(2) (OXD-N) added at meta-substitution in the phenyl ring are presented. The ground state structures of the title complexes are optimized at B3LYP/6-31G level of theory. In addition, the time dependent density functional theory (TDDFT) method is applied to calculate the absorption and emission spectra of the derivatives based on the ground state geometries. Comparing with the alkoxy substituents, the results show that the electron-withdrawing substituents have remarkable influences on the energy levels of the frontier molecular orbitals, the spectra and the transition compositions. Especially, -NO(2) group plays the prominent role and the fluorine improves the energy level of LUMO further. The experimental absorption wavelengths for OXD-X, OXD-A3 and OXD-A7 are well reproduced by the TDDFT technique. Moreover the absorption wavelengths and the transition compositions can be effectively adjusted through introducing electro-withdrawing groups in the phenyl ring. The reorganization energies for hole and electron are smaller than that of typical hole and electron transport materials.

Theoretical study on C60-doped polyacenic semiconductor (PAS) through phosphorylation

In this paper, theoretical study on P n C 60 /(P n+ ) n C 60 endohedral and exohedral complexes for n=1-4 was performed by semiempirical and Hartree-Fock quantum chemical calculations. This study reveals the energetics that a P is inclined to stay outside of the carbon cage. The interaction between P/P + and C 60 is depicted when the phosphorylated polyacenic semiconductor (PAS) is doped with a certain proportion of C 60 .

NOVEL ANODE Li-ION SECONDARY BATTERIES DERIVED FROM NANOCRYSTALLINE Li4Ti5O12/POLYACENE MATERIALS

Spinel lithium titanate (Li4Ti5O12), shown to be a superior anode material for energy storage battery, has attracted a great deal of attention because of the excellent Li-ion insertion and extraction reversibility. The high rate characteristics must be amplified before large scale production. A method to overcome this is to prepare electrode materials coated with carbon. A Li4Ti5O12/Polyacene (PAS) composite were first prepared via an in situ carbonization of phenol-formaldehyde (PF) resin route using TiO2-anatase, Li2CO3, and PF resin as precursors by a solid-state reaction. With increasing the current density, the sample still keeps the excellent cycle performance.

Li x C n as Anode Material for Lithium Ion Batteries

We design a way that the anode hosts provide lithium ion in lithium ion battery operation. If the limiting factors of the cathode materials are less, there will be more alternatives for it. It was proven to be successful by two kinds of test cells based on Li x C n as anode material, and β-FeOOH or Cr 8 O 21 as cathode materials. Their theoretical capacities are much higher than those present electrode materials. Unlike the lithium secondary batteries with lithium metal foil or lithium alloy as anode, this type of lithium ion batteries with Li x C n as anode prohibit dendrite formation during charging-discharge process. The idea of lithium ion sources coming from the anode can come true successfully as a result that steady protecting solution be sought for Li x C n .