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Modelling of charge carrier transport in conjugated polymers doped by polar additives

Toman P., Nešpůrek S., Bartkowiak W.

Materials Science Poland

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2009

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Vol. 27, No. 3

797--812

EN

A theoretical model of the inter-chain charge carrier transport in poly[2-methoxy-5-(2´-ethylhexyloxy)- p-phenylene vinylene] doped with a photochromic polar additive is put forward. The model attributes to each polymer chain a set of charge states, in which charge carriers thermalize. These on-chain states are calculated by solving the Schrodinger equation with a tight binding Hamiltonian. The interchain transfer rates are determined using the Marcus formula. The model describes the effect of polar additives on charge carrier transport. The presence of the additives results in a decrease of charge mobility, because of the increase of the local energy disorder. A decrease of the inter-chain mobility by up to several orders of magnitude is found if the width of the local energy disorder is doubled. This finding confirms the possibility of constructing an optoelectrical switch based on a polymer doped with a photochromic polar additive.

2

Electronic and gas sensing properties of soluble phthalocyanines

Pochekailov S., Rais D., Nešpůrek S., Rakušan J., Karásková M.

Materials Science Poland

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2009

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Vol. 27, No. 3

781--795

EN

Some optical and electrical properties of 3-diethylamino-1-propylsulfonamide substituted zinc and metal-free phthalocyanines are presented. These materials are sensitive to NO2 even at concentrations as low as 0.1-2.5 ppm. Electrical conductivity and photoconductivity were used as the detection methods.

3

Electrical conductivity in thin films fabricated from nanoparticles of a polymeric composite based on PEDOT

Rais D., Hain J., Pich A., Pochekailov S., Nešpůrek S., Adler H. J. P., Hamáček A., Řeboun J.

Materials Science Poland

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2009

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Vol. 27, No. 3

769--780

EN

A comparative study of electrical properties of films fabricated from a series of polymeric core shell particles and microgels is presented. The core shell particles consist of spherical polystyrene core covered by electrically conductive poly[3,4-(ethylenedioxy)thiophene] (PEDOT). Microgels are composed of PEDOT grains embedded into crosslinked, electrically insulating polymer bodies. The electrical resistivity of the films changes from 12 G?ˇcm to 100 ?ˇcm; the value depends on the thickness of the shell cover and the type of oxidant used for PEDOT polymerization. Electrical conductivity in the films of core shell particles is thermally activated and obeys the inverse Meyer-Neldel rule, which indicates that the electrical conductivity is governed by a common transport mechanism. Electrical conductivity depends, among others, on the humidity in the surrounding environment. In films consisting of particles with a high PEDOT content (and thus high conductivity) the resistivity increases as the humidity increases. Conversely, when the films are formed from particles having a low PEDOT content, the humidity has a reverse effect. An explanation for this behaviour is proposed. The frequency dependences of ac conductivities of high conductivity "core shell" and "microgel" films suggest existence of hopping charge carrier transport mechanism for large humidity scale.

4

Spectroscopic, Studies of Two Dynamicallly Different 1,4-Dihydropyridine Structures

Śliwińska E., Palewska K., Lewanowicz A., Lipiński J., Sworakowski J., Gancarz R., Nešpůrek S.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 2-3

235-247

EN

Results of spectroscopic studies of solutions of two photoactive dihydropyridine derivatives: 1-methyl-2,4,4,6-tetraphenyl-1,4-dihdyropyridine and 4,4-(biphenyl-2,2_-diyl)- 2,6-diphenyl-1-methyl-1,4-dihydropyridine (hereafter referred to as DHP and BDH, respectively) are presented. The analysis of UV-Vis and NMR spectra points to a different behaviour of the two molecules under study, in spite of a close similarity of formal molecular structures. These results indicate that two isomers of BDH exist in solid matrices, as well as in liquid solutions, in the temperature range studied. No such feature has been detected in DHP.We attribute the difference to an enhanced stiffness of the BDH molecule resulting from a bridge between side phenyl groups.

5

Photoconductivity and Photodielectric Properties of Diethyl 2,5-Dianilinoterephthalale Films

Nešpůrek S., Mačkus P.K.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 2-3

443-456

EN

Photoelectric and photodielectric properties of thin films of diethyl 2,5-dianilinoterephthalate were studied. Both phenomena are strongly influenced by charge carrier trapping. A weak photodielectric response (about 0.5% and 0.01% at the frequencies 102 and 104 Hz, respectively) seems to be associated with the photoformation of free and trapped charge carriers.