Dopant induced anomalous field dependent mobility behavior of poly(3-octylthiophene) devices

Singh, WJ and Singh, KJ and Ramesh, KP and Devi, KN (2021) Dopant induced anomalous field dependent mobility behavior of poly(3-octylthiophene) devices. In: Synthetic Metals, 279 .

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Abstract

Temperature dependent DC current-voltage (I-V) down to 50 K and field-dependent AC impedance measurements were carried out to study the electric field and temperature dependence of charge carrier mobility in Poly(3-octylthiophene) based metal/polymer/metal device structures of different charge carrier concentrations. In highly doped device, a negative field-dependent mobility (NFDM) which vanishes below 150 K was observed whereas a positive field-dependent mobility (PFDM) was observed in moderately doped devices. The observed NFDM is attributed to the low energetic disorder and high positional disorder in the highly doped devices. With further lowering of carrier concentration, charge carrier mobility first decreases with the increase in applied field attaining a minimum value and then increases with the applied field. At higher temperatures (T>150K), all the three devices show thermally-activated process and activation energy increases with lowering the charge carrier concentrations indicating that doping level plays important role in thermally activated transport mechanism. However, in lower temperature (T<100K), activation energy is almost independent of doping level suggesting that injected carrier plays an important role in the lower temperature region. Data from AC impedance measurement also supports the field-dependent mobility model of conduction mechanism in the devices. Analysis of the AC impedance data of the three devices reveals that the equivalent circuit of highly and moderately doped devices is different from that of the low carrier concentration device. The presence of highly energetic disorder in low carrier concentration devices is also confirmed from AC impedance analysis. © 2021 Elsevier B.V.

Item Type:	Journal Article
Publication:	Synthetic Metals
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Elsevier Ltd
Keywords:	Activation energy; Carrier concentration; Carrier mobility; Carrier transport; Charge transfer; Electric fields; Electric impedance measurement; Equivalent circuits; Temperature distribution, A.C. impedance; AC impedance measurement; AC-impedance; Charge-carrier mobility; Doped devices; Field-dependent mobility; Poly(3-octylthiophene); Poly3-octylthiophene; SCLC mechanism, Electric impedance
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	21 Sep 2021 09:33
Last Modified:	21 Sep 2021 09:33
URI:	http://eprints.iisc.ac.in/id/eprint/69782

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