Exploiting the electrical properties of thin films of semiconducting polymers

Abstract

A brief review is provided of the ways electrical properties of semiconducting polymers can be exploited. Emphasis is given to the analysis of electrical conductivity data, in particular to the importance of interchain processes that must be considered along with intrachain processes for bulk conductivity. Among the large variety of possible applications of thin lms of semiconducting polymers, the focus is placed on recent breakthroughs in producing diodes, eld e ect transistors and electroluminescent devices out of these materials. The fabrication of ultrathin lms from semiconducting polymers, using the Langmuir-Blodgett and the self-assembly techniques, is discussed to illustrate the importance of processibility issues for any real application including these polymers. I IntroductionDue to their remarkable intrinsic electrical insulating characteristics, organic polymeric materials have been for a long time the subject of extensive dielectric and charge storage studies 1-3 . Electrical breakdown, charging-discharging mechanisms, thermoelectric and radiation e ects, and dielectric relaxation processes have been investigated from both experimental and theoretical points of view. Insulating polymers are now widely used as insulation in power cables in energy distribution networks, and in di erent t ypes of high accuracy equipment. The contribution of Prof. B. Gross in this area started at the early 70s, when he introduced uorinated polymers as extremely good electrets owing to their large charge storage capacity and remarkable mechanical properties 4 . The combination of such properties allowed these polymers to be applied as active membranes in electroacoustic devices 5 . Later on the family of polyvinylidene uoride PVDF found several applications as piezoelectric and pyroelectric devices, deriving from their ferroelectric activity 6 .Until the early 1980s, most studies and applications using electrical properties of polymeric materials only exploited their insulating and charge storage capabilities. A new turn, both in science and technology, t o o k place in the 1980s with the advent of the conducting and semiconducting polymers 7 , with polyacetylene being their foremost representative in the initial studies 8 . Several possible applications have since been suggested and actually demonstrated in which the polymer is employed not only as a passive, insulating element, but also with an active role, as in microelectronic device components 9 .One major di culty, which i s e v en now a stumbling block for the widespread use of conducting polymers, is fabrication in the required form and shape. The rst conducting polymers produced were almost invariably insoluble and infusible. Over the years, new approaches have been implemented by v arious research groups in order to overcome the fabrication di culty. Such approaches stem from synthetic chemistry methods 10 with incorporation of side groups that make the polymer soluble, new techniques for growing lms electrochemically 11 and the use of functionalized acids to im...

1/fnoise in Langmuir–Blodgett films on silicon

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The Photo-Electrical Behavior of n-Si and p-Si/Orange Dye/ Conductive Glass Cells

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Preparação e caracterização de sensores de amônia baseados em filmes ultrafinos de polianilina e polianilina-ftalocianinas.

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