Semiconductor organic

There are hundreds of semiconductor materials, but silicon alone accounts for tire overwhelming majority of tire applications world-wide today. The families of semiconductor materials include tetraliedrally coordinated and mostly covalent solids such as group IV elemental semiconductors and III-V, II-VI and I-VII compounds, and tlieir ternary and quaternary alloys, as well as more exotic materials such as tire adamantine, non-adamantine and organic semiconductors. Only tire key features of some of tliese materials will be mentioned here. For a more complete description, tire reader is referred to specialized publications [6, 7, 8 and 9]. 

Semiconductors are materials that are characterized by resistivities iatermediate between those of metals and of iasulators. The study of organic semiconductors has grown from research on conductivity mechanisms and stmcture—property relationships ia soHds to iaclude appHcations-based research on working semiconductor junction devices. Organic materials are now used ia transistors, photochromic devices, and commercially viable light-emitting diodes, and the utility of organic semiconductors continues to iacrease. 

The study of organic semiconductors and conductors is highly iaterdisciplinary, involving the fields of chemistry, soHd-state physics, engineering, and biology. This article provides a treatment of the theoretical aspects of organic semiconductors as well as an overview of recent advances ia the field and the uses of these materials based on their conductive and optical properties. 

Table 1. Common Donor and Acceptor Molecules Used in Organic Semiconductor and Devices...

Physical Properties Electrical. Electrical properties have been the main focus of study of organic semiconductors, and conductivity studies on organic materials have led to the development of materials with extremely low resistivities and large anisotropies. A discussion of conductivity behaviors for various classes of compounds follows. 

The highly conductive class of soHds based on TTF—TCNQ have less than complete charge transfer (- 0.6 electrons/unit for TTF—TCNQ) and display metallic behavior above a certain temperature. However, these soHds undergo a metal-to-insulator transition and behave as organic semiconductors at lower temperatures. The change from a metallic to semiconducting state in these chain-like one-dimensional (ID) systems is a result of a Peieds instabihty. Although for tme one-dimensional systems this transition should take place at 0 Kelvin, interchain interactions lead to effective non-ID behavior and inhibit the onset of the transition (6). 

Table 2. Representative Polymers Used for Organic Semiconductors and Metals...

Selenium is an essential element and is beneficial at low concentrations, serving as an antioxidant. Lack of selenium affects thyroid function, and selenium deficiencies have been linked to Keshan Disease (34). Selenium at high levels, however, is toxic. Hydrogen selenide (which is used in semiconductor manufacturing) is extremely toxic, affecting the mucous membranes and respiratory system. However, the toxicity of most organ oselenium compounds used as donor compounds for organic semiconductors is not weU studied. 

H. Meier, Organic Semiconductors, Vedag Chemie, Weinheim, Germany, 1974. 

ITPAIS classification Silver hahde ZnO TiO ZnS Se CdS, CdSe Misc. organic semiconductor... 

Table 2. Spectral Sensitizers for Inorganic and Organic Semiconductors...

J. Janata, Phys.Chem.Chem.Phys., 5 (2003) 5155-5158 Organic Semiconductors in Molecular Electronics ... 

ORGANIC SEMICONDUCTOR THIN-FILM TRANSISTOR SENSORS... 

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