1023-1935/04/4003- © 2004 åÄIä “Nauka /Interperiodica” 0359 Russian Journal of Electrochemistry, Vol. 40, No. 3, 2004, pp. 359–363. Translated from Elektrokhimiya, Vol. 40, No. 3, 2004, pp. 403–407. Original Russian Text Copyright © 2004 by Tameev, He, Milburn, Danel, Tomasik, Vannikov. INTRODUCTION The increasing interest in the electronic phenomena in polymer systems is caused by the results achieved recently in practical applications of polymer layers as photosensitive elements in electrophotographic (dupli- cators, laser printers) [1] and electroluminescent (light- emitting diodes) [2] devices. Solar batteries based on organic materials also are becoming promising for practical use [3]. In all of the above devices, the trans- port of charge carriers is the key factor determining fast operation of electrophotographic apparatus and the power conversion efficiency. The charge-carrier transport through a polymer layer involves successive charge transfer between neighboring transport centers. The transfer is a redox reaction between a neutral molecule and its radical cat- ion (hole transport) or radical anion (electron transport) [4]. In most of charge-transport polymer systems, the hole charge carriers are mobile. The electron transport occurs in some polymer photoconductors, for example, aromatic polyimide [5] and derivatives of polyphe- nylene vinylene [6]. The electron transport can be also provided by low-molecular compounds like aluminum hydroxyquinoline (Alq) [7] and derivatives of pyrazole pyridine or pyrazole quinoline [8, 9]. Here, we will study the electron transport in copolymer films with the pyrazolyl groups in the side or main chain of the mac- romolecule. EXPERIMENTAL Figure 1 gives structural formulas for copolymers (CP) under study. Copolymers CP-1, CP-2, and CP-3, which contain pyrazoline derivatives in the side chain, were synthesized of relevant vinyl or methacrylate monomers. Copolymers CP-4 and CP-5, which contain pyrazoline in the main chain, were synthesized using a polycondensation method. The production of mono- mers and their subsequent polymerization were described in [10]. The drift mobility of electrons in polymer layers is usually determined using the known time-of-flight experiment [1]. The peculiarity of time-of-flight mea- surements consists of the following. A specimen is con- structed on the model of a parallel-plate capacitor (“sandwich”): a layer of the polymer under investiga- tion and a photogenerating layer are placed between two electrodes. In the measuring circuit, one electrode of the specimen is connected to a dc source and another electrode, to a recorder. A short pulse of light is com- pletely absorbed in the generating layer and photoge- nerates charge carriers. Then, depending on the direc- tion of the applied field, holes or electrons are injected into the polymer layer. The charge carriers start to drift to the counterelectrode as a narrow package, because under the experimental conditions the thickness of the generating layer is much smaller than that of the poly- mer layer and the pulse length is much shorter than the characteristic time of the transit of the charge carriers through the layer. The observed transient-current sig- nals permit the determination of the drift mobility of charge carriers and the dispersion of their velocity. Drift Mobility of Electrons in Pyrazoline-Containing Copolymers A. R. Tameev a,z , Z. He b , G. H. W. Milburn c , A. Danel d , P. Tomasik d , and A. V. Vannikov a a Frumkin Institute of Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119071 Russia b Institute of Optoelectronic Technology, Beijing Jiaotong University, 100044 China c Napier University, Colinton Road 10, Edinburgh, EH10 5DT UK d Chemical Department, University of Agriculture, Krakow, 31129 Poland Received March 26, 2003 Abstract—Drift mobility of electrons in copolymers containing pyrazolyl fragment in the main or side chain of the copolymer is studied experimentally using the time-of-flight method. The mobility is an exponential func- tion of the applied electric field, and its values for the copolymers range from 5 × 10 –7 to 2 × 10 –5 cm 2 V –1 s –1 at the field strength ranging from 5 × 10 4 to 1 × 10 6 V cm –1 . Based on the measured mobilities and the molecule parameters, which were obtained by a PM3 quantum-chemical calculation, the role of copolymer fragments in the transport of charge carriers is discussed. Key words: mobility of electrons, thin polymer film z Corresponding author, e-mail: altam@online.ru