224 Current Physical Chemistry, 2012, 2, 224-240 Conducting Polymers and their Applications Murat Ates a, * , Tolga Karazehir a and A. Sezai Sarac b a Department of Chemistry, Faculty of Arts and Sciences, Namik Kemal University, Degirmenalti Campus, 59030, Tekirdag, Turkey; b Department of Chemistry, Istanbul Technical University, Polymer Science and Technology, Maslak, 34469, Istanbul, Turkey Abstract: This review article focuses on conducting polymers and their applications. Conducting polymers (CPs) are an exciting new class of electronic materials, which have attracted an increasing interest since their discovery in 1977. They have many advantages, as compared to the non-conducting polymers, which is primarily due to their electronic and optic properties. Also, they have been used in artificial muscles, fabrication of electronic device, solar energy conversion, rechargeable batteries, and sensors. This study comprises two main parts of investigation. The first focuses conducting polymers (polythiophene, polyparaphenylene vinylene, polycarbazole, polyaniline, and polypyrrole). The second regards their applications, such as Supercapacitors, Light emitting diodes (LEDs), Solar cells, Field effect transistor (FET), and Biosensors. Both parts have been concluded and summarized with recent reviewed 233 references. Keywords: Biosensor, Conducting polymer, Field Effect Transistor, Light Emitting Diode, Solar Cell, Supercapacitor. 1. CONDUCTING POLYMERS Since the discovery of the conducting polymers in the late 1970s, many scientists have been working on finding applications for the newly discovered conducting polymers, such as thin film transistors [1], polymer light emitting diodes (LEDs) [2], corrosion resistance [3], electromagnetic shielding [4], sensor technology [5], molecular electronics [6], supercapacitors [7], and electrochromic devices [8]. By judiciously choising the molecule combinations, it is possible to prepare multifunctional molecular structures that open possibilities for almost any desired applications. 1.1. Poly(thiophene) Polythiophene has received great scientific attention in the last twenty years. This fact has been made possible by its interesting properties, such as good environmental and thermal stability, as well as by its wide application perspectives [9]. Numerous polyalkyl derivatives of thiophene have been synthesized so far by chemical and electrochemical approaches, resulting in conducting polymers with better solubility and higher capacitor behaviors [10]. Conducting polymers have attracted attention to be used as electrochromic materials due to their inexpensive and potentially processable nature [11-13]. Thiophene-based polymers have received significant interest for their electrical properties, environmental stabilities, and a number of practical applications. For instance, these materials have been used as charge dissipation coatings in electron-beam lithography [14] and as an active semiconducting material in organic thin-film transistors [15]. Recently, Shi and co- workers reported the preparation of polythiophene films *Address correspondence to this author at the Department of Chemistry, Faculty of Arts and Sciences, Namik Kemal University, Degirmenalti Campus, 59030, Tekirdag, Turkey; Tel: +90 282 2933866 (236); Fax: +90 282 2934149; E-mail: mates@nku.edu.tr from a boron trifluoride-diethyl ether solution with thiophene monomer by electrochemical means so that the films possess tensile strength, are tougher and mechanically more durable than aluminum [16]. Thiophene based polymers can also be used as potential materials for electrochromic devices [17]. An electrochromic material possesses ability to reversibly change color by altering its redox state. For instance, poly(3- methylthiophene) (poly(3MTh)) is known to be blue in the oxidized state and red in the reduced state. Panero et al. have investigated the electrochromic devices by using poly(3MTh) coated indium tin oxide (ITO) glass electrodes, and thus have obtained an optical contrast between the reduced and oxidized states of about 30 % [18]. 1.2. Poly(para-phenylene Vinylene) Poly(para-phenylene vinylene) (PPV) is a conducting polymer of the rigid-rod polymer family with high levels of crystallinity. PPV is an important polymer in many electronic applications, such as LEDs and photovoltaic devices [19], which is due to the small optical band gap and its bright yellow fluorescence. In addition, it can be easily doped to form electrically conductive materials. Therefore, its electronic and physical properties can be changed by the inclusion of functional groups. It is mostly synthesized via chemical routes, where a precursor is converted to PPV by thermal elimination of leaving group. The deposition of PPV onto or inside polysilicon (PSi) could lead to the development of new functional hybrid devices. In literature, PPV and poly(2,5-dimethyl-para-phenylene vinylene) were prepared via the formation of a double bond by thermal elimination of an octylsulfinyl side group at 200 0 C under vacuum [20]. Alves et al. have studied theoretical approaches of PPV and poly(p-phenylene) (PPP) [21]. PPV- based devices have drawbacks due to photodegradation. However, PPV and its derivatives find frequent application in research cells [22]. 1877-94 /12 $58.00+.00 © 2012 Bentham Science Publishers