Study on electrical transport and photoconductivity in iodine-doped cellulose fibers A. S. Zakirov • Sh. U. Yuldashev • H. J. Wang • J. C. Lee • T. W. Kang • A. T. Mamadalimov Received: 23 June 2010 / Accepted: 14 August 2010 / Published online: 8 September 2010 Ó Springer Science+Business Media, LLC 2010 Abstract The electrical transport and photoconductivity of pure and iodine-doped cellulose fibers have been stud- ied. The studies were conducted in the temperature range 293–363 K, while the electric field was varied over the range 1–100 V cm -1 . The conductivity of the iodine- doped cellulose fibers shows significant enhancement by more than four orders of magnitude as compared to undoped samples. The analysis reveals that the electrical conduction follows Ohm’s law for iodine-doped samples, while for the undoped samples the bulk-limited Pool– Frenkel conduction mechanism is likely to dominate for the steady state current. Especially, the clear photoconduction response at UV and visible region indicates that photo- conduction is essential due to band-to-band electron–hole pair’s generation and that doped CF is a good conductor of photogenerated carriers. Introduction Electrical conduction in polymers has been studied exten- sively during the past two decades to understand the nature of charge transport in these materials [1–3]. The elucidation of the charge injection and carrier migration processes will become essential for the future use of these materials. The conduction mechanism is mainly charac- terized by the transport parameters, such as charge carrier density and charge carrier mobility. Considerable interest has been shown on the effect of doping on the transport properties of polymers [4–6]. Chemical, photochemical, or electrochemical doping is used to introduce extrinsic charge carriers into organic semiconductors [7–9]. Depend- ing on their chemical structure and the way, in which they react with the macromolecular matrix, doping substances decrease the resistivity of the polymers to different degrees [10]. The natural cotton fibers offer wide possibilities in this regard. These cellulosic fibers (CFs) may be considered to be polycrystalline materials with much smaller particle size and relatively larger fraction of grain boundaries. More- over, the CF is supposed to have different morphology with respect to processing conditions [11]. The reason for such a variation, even though these are made up of same chemical units, lies in the fact that the number of inter- and intra- weak hydrogen bonds like C–HO, O–HO, and N–HO determines the extent of ordering in the CF [12]. As the processing conditions vary, the morphology of the resulting cellulose fibers may change. This will lead to the change in the physical properties of the resulting materials [13]. Many research groups have been studying these modifi- cations using different approaches which include a variety of chemical treatments, grafting, couplings between fiber and matrix, and physical coverage of the fibers by a polymer sleeve [14]. Most studies have been focused on in situ polymerization to produce conductive cotton fabric since this method does not require the destruction of the substrate and provides reasonably good conductivity [15]. Its electrical conductivity and charge-storage capability can A. S. Zakirov  Sh. U. Yuldashev  H. J. Wang  J. C. Lee  T. W. Kang (&) Quantum-Functional Semiconductor Research Center, Dongguk University, Seoul 100715, Republic of Korea e-mail: twkang@dongguk.edu A. S. Zakirov  Sh. U. Yuldashev Department of Thermophysics, Academy of Sciences, Tashkent 100135, Uzbekistan A. T. Mamadalimov Department of Physics, National University of Uzbekistan, Tashkent 100175, Uzbekistan 123 J Mater Sci (2011) 46:896–901 DOI 10.1007/s10853-010-4832-6