Minicurso - Electrochemical and spectroelectrochemical analysis of organic compounds: modern application of organic semiconductors

Prof. Przemyslaw Data (Faculty of Chemistry, Salesian University of Technology, Gliwice and Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Zabrze - Poland) Nowadays, the very rapid pace of development of numerous fields of study is observed, the driving force of which are the newest discoveries in the field of physics and chemistry. These fields include the modern electronics, which, due to the development in the field of semiconductors, and due to the discoveries and understanding of numerous phenomena occurring on the quantum level, newly developed, better materials, has been set on the path of extremely dynamic development. Apart from the typical conductive materials, such as metals and their alloys, as well as silicon and mixed oxides of transition metals, conductive polymers exhibit numerous interesting and atypical effects, making them irreplaceable components of electronic elements. An increasing role of organic materials with specific chemical structure is observed, i.e. possessing conjugated π bond systems, referred to as “organic or synthetic metals” due to their numerous interesting properties. One of such properties with great practical importance is the possibility to attribute them with electric conductivity under specific conditions, the level of which at the current development state may assume values exhibited by certain less conductive metals. Nowadays, conjugated organic compounds have been widely applied in electronics, creating a new branch of industry - organic electronics, which, in some cases, displaces typical inorganic semiconductors. From the historical viewpoint, conductive polymers were discovered accidentally. At the beginning of 1970, Hideki Shirakawa by accidentally adding “thousand-fold” too much catalyst to the reactor, synthesized film on the basis of trans-polyacetylene. At the same time, another chemist, Alan G. MacDiarmid, and a physicist Alan Heeger experimented with a metal-like film based on an inorganic sulfur nitrite polymer. In 2000, the Nobel Prize in chemistry was awarded to three scientists working on conductive polymers: Alan Heeger, Alan G. MacDiarmid and Hideki Shirakawa. At the moment of the discovery of conductive polymers, a great boom in the use of these compounds in organic electronics began. Similarly to 1950s, when people imagined computers in every home, scientists theorized on the possible applications of these materials, from plastic cables to flexible integrated circuits. Therefore, organic electronics is often referred to as flexible electronics, and it is a very rapidly developing field of science and industry. Every day, scientist are synthesizing hundreds of new compounds which need to be evaluated for the optoelectronic purpose. From one side the problem is how to screen for suitable materials where the quantum chemical calculations give quite limited results. On the other side, it’s important for organic electronics to understand the processes occurring in the organic compounds. Nowadays, electrochemical measurements are one of the cheapest techniques to use for analysis conjugated compounds which show practical results. Information obtained through electrochemical and spectroelectrochemical analysis may be extrapolated giving a chance to screen many compounds in short time. In order to understand the objective of the analysis and the conclusions drawn, one must look at the very source of the device operation and then the effects, which are to be performed by the given device. In the case of operation source, all that is considered are the effects taking place in the material under the influence of the flow of charges generated by the applied voltage and therefore electrochemical studies are of such great importance. Electrochemical research enables the study of material under conditions similar to those of an operating device. And the combination of electrochemical and spectroscopy methods enable clear identification of the processes occurring in the tested material. The purpose of this lecture is to show types of organic electronics devices and the connection between structure and application and how to use electrochemistry to screen the organic materials.

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