Self-organised poly[(ethynediyl)(arylene)(ethynediyl)silylene]/<Emphasis Type="Italic">N</Emphasis>-ethylcarbazole/polyphenylsilsesquioxane hybrid nanomaterials: photoconductivity and electro-optic response at telecommunication wavelengths

The photoconductivity and electro-optic response of a self-organised nanostructured poly[(ethynediyl)(arylene)(ethynediyl)silylene]/N-ethylcarbazole/polyphenylsilsesquioxane composite have been investigated with a cw diode laser at a wavelength of 1500 nm. For electric field 25 V µm^–1 and beam intensity 18 W cm^–2, the photosensitivity was 0.5 pS cm^–1 (W cm^–2)^–1. The dark conductivity was found to be much less than the photoconductivity and the composite shows photo charge generation at this wavelength. The value of the composite electro-optic coefficient is in agreement with data for polymeric materials active in the visible range. Orientational effects have been observed with modulation frequencies down to several Hz, and quite slow dynamics of the response can be expected.Based on the report presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (Moscow, May 30–June 4, 2004).Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1897–1901, September, 2004.     

Influence of molecular weight on the short‐channel effect in polymer‐based field‐effect transistors

In this study, we demonstrate how the intrinsic properties of a polymer can influence the electrical characteristics of organic field‐effect transistors (OFETs). OFETs fabricated with three batches of poly[2‐methoxy,5‐(3′,7′‐dimethyl‐octyloxy)]‐p‐phenylene vinylene (MDMO‐PPV) were investigated. The properties of the polymers were initially investigated using Fourier transform infrared spectroscopy (FTIR), impedance spectroscopy (IS), gel permeation chromotography (GPC), and cyclic voltammetry (CV), respectively. The structure and purity of the polymer batches were found to be very comparable, but the molecular weight (M_n and M_w) and polydispersity (PDI = M_w/M_n), varied between the samples and the HOMO and LUMO levels of the polymers were found to depend on the molecular weight properties. OFETs were then fabricated with the polymers and electrically characterized. It was observed that the channel current and the field‐effect mobility increase with increasing polymer molecular weight. The output characteristics of the transistors, on the other hand, were found to depend on the PDI of the polymer. Saturation of the channel current occurs at higher source–drain voltages and short‐channel behavior was observed to start at longer channel lengths for polymers with a higher PDI. This behavior is observed to be thickness dependent, and the short‐channel behavior was more pronounced for thicker MDMO‐PPV films. These results are explained in terms of influences of chain packing and ordering and high bulk currents on the FET output and transistor parameters. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 117–124, 2012     

Charge transport in polyaniline doped with 3-nitro-1,2,4-triazol-5(4H)-one

Polyaniline (PANI) base was protonated in aqueous solutions of an organic acid, 3-nitro-1,2,4-triazol-5(4H)-one (NTO). The temperature dependence of DC conductivity of PANI-NTO seems to correspond to the theory of variable range hopping (VRH) in three dimensions. The frequency dependence of AC conductivity also reflects the hopping nature of mobile charges. The activation energy for the polymers with protonation degree above 0.12 remains constant with increasing dopant concentration and DC conductivity. The value of this constant may correspond to the energy needed for the ionization of dopant counterion. The fit of the electric relaxation function to the stretched exponential function ϕ(t) = exp[−(t/τ)^β] gives the stretch parameter β about 0.35, which shows that the distribution of relaxation times is broad and indicates a high inhomogeneity in the distribution of a dopant.     

含四-苯基卟啉基团聚酰亚胺膜的光电导性能研究

分剐以均苯四酸二酐(PMDA)与四(4-氨基苯基)卟啉(TAPP)／4，4′-二苯醚(ODA)、TAPP／3，6-二氨基-N-甲基咔唑(DACz)聚合得到两个系列含四-苯基卟啉基团(TPP)聚酰亚胺(PI)共聚膜，并时其作为载流子发生层(CGL)制成的感光体的光电导性能进行了测试。结果表明：PI共聚膜的光电导性能随分子链中TPP基团含量的提高而增强；当TPP基团含量相同时，PMDA／TAPP／ODA系列的光电导性能较PMDA／TAPP／DACz系列好；含TPP基团PI共聚膜的光电导性能明显优于四-苯基卟啉分子掺杂体系；在CGL与导电铝基间引入聚甲基丙烯酸甲酯(PMMA)阻挡层(CBL)不能提高感光体的光电导性能。从光电导机理分析了TPP基团、四-苯基卟啉分子的聚集结构与PI膜光电导性能的关系。     

Polarizable Atomistic Calculation of Site Energy Disorder in Amorphous Alq3

A polarizable molecular dynamics simulation and calculation scheme for site energy disorder is presented in amorphous tris(8‐hydroxyquinolinato)aluminum (Alq₃) by means of the charge response kernel (CRK) method. The CRK fit to the electrostatic potential and the tight‐binding approximation are introduced, which enables modeling of the polarizable electrostatic interaction for a large molecule systematically from an ab initio calculation. The site energy disorder for electron and hole transfers is calculated in amorphous Alq₃ and the effect of the polarization on the site energy disorder is discussed.     

Sensitization of Photoconductivity in Polymeric Compositions with Fe2O3 and CdS Nanoparticles by an Organic Compound with Intramolecular Charge Transfer

The electric conductivity and photoconductivity of films based on polyvinylbutyral and containing Fe₂O₃ and CdS nanoparticles and an organic compound with intramolecular charge transfer as photoconductivity sensitizer in the visible and near infrared regions were investigated. In the absorption region of the sensitizer the activation energy of the photocurrent is somewhat greater than 0.1 eV and is close to the activation energy of the electric conductivity current.