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Organic electronics is a field of materials science concerning the design, synthesis, characterization, and application of organic molecules or polymers that show desirable electronic properties such as conductivity. Unlike conventional inorganic conductors and semiconductors, organic electronic materials are constructed from organic (carbon-based) molecules or polymers using synthetic strategies developed in the context of organic chemistry and polymer chemistry.
An organic light-emitting diode, also known as organic electroluminescentdiode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This organic layer is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, and portable systems such as smartphones and handheld game consoles. A major area of research is the development of white OLED devices for use in solid-state lighting applications.
Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity. Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conductive polymers is their processability, mainly by dispersion. Conductive polymers are generally not thermoplastics, i.e., they are not thermoformable. But, like insulating polymers, they are organic materials. They can offer high electrical conductivity but do not show similar mechanical properties to other commercially available polymers. The electrical properties can be fine-tuned using the methods of organic synthesis and by advanced dispersion techniques.
Poly(p-phenylene vinylene) is a conducting polymer of the rigid-rod polymer family. PPV is the only polymer of this type that can be processed into a highly ordered crystalline thin film. PPV and its derivatives are electrically conducting upon doping. Although insoluble in water, its precursors can be manipulated in aqueous solution. The small optical band gap and its bright yellow fluorescence makes PPV a candidate in applications such as light-emitting diodes (LED) and photovoltaic devices. Moreover, PPV can be doped to form electrically conductive materials. Its physical and electronic properties can be altered by the inclusion of functional side groups.
Organic semiconductors are solids whose building blocks are pi-bonded molecules or polymers made up by carbon and hydrogen atoms and – at times – heteroatoms such as nitrogen, sulfur and oxygen. They exist in form of molecular crystals or amorphous thin films. In general, they are electrical insulators, but become semiconducting when charges are either injected from appropriate electrodes, upon doping or by photoexcitation.
poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is a polymer mixture of two ionomers. One component in this mixture is made up of sodium polystyrene sulfonate which is a sulfonated polystyrene. Part of the sulfonyl groups are deprotonated and carry a negative charge. The other component poly(3,4-ethylenedioxythiophene) (PEDOT) is a conjugated polymer and carries positive charges and is based on polythiophene. Together the charged macromolecules form a macromolecular salt.
Pentacene is a polycyclic aromatic hydrocarbon consisting of five linearly-fused benzene rings. This highly conjugated compound is an organic semiconductor. The compound generates excitons upon absorption of ultra-violet (UV) or visible light; this makes it very sensitive to oxidation. For this reason, this compound, which is a purple powder, slowly degrades upon exposure to air and light.
Fluorene, or 9H-fluorene is an organic compound with the formula (C6H4)2CH2. It forms white crystals that exhibit a characteristic, aromatic odor similar to that of naphthalene. It has a violet fluorescence, hence its name. For commercial purposes it is obtained from coal tar. It is insoluble in water and soluble in many organic solvents. Although sometimes classified as a polycyclic aromatic hydrocarbon, the five-membered ring has no aromatic properties. Fluorene is mildly acidic.
Photothermal therapy (PTT) refers to efforts to use electromagnetic radiation for the treatment of various medical conditions, including cancer. This approach is an extension of photodynamic therapy, in which a photosensitizer is excited with specific band light. This activation brings the sensitizer to an excited state where it then releases vibrational energy (heat), which is what kills the targeted cells.
Polydioctylfluorene (PFO) is an organic compound, a polymer of 9,9-dioctylfluorene, with formula (C13H6(C8H17)2)n. It is an electroluminescent conductive polymer that characteristically emits blue light. Like other polyfluorene polymers, it has been studied as a possible material for light-emitting diodes.
A silsesquioxane is an organosilicon compound with the chemical formula [RSiO3/2]n. Silsesquioxanes are colorless solids that adopt cage-like or polymeric structures with Si-O-Si linkages and tetrahedral Si vertices. Silsesquioxanes are members of polyoctahedral silsesquioxanes ("POSS"), which have attracted attention as preceramic polymer precursors to ceramic materials and nanocomposites. Diverse substituents (R) can be attached to the Si centers. The molecules are unusual because they feature an inorganic silicate core and an organic exterior. The silica core confers rigidity and thermal stability.
A light-emitting electrochemical cell is a solid-state device that generates light from an electric current (electroluminescence). LECs are usually composed of two metal electrodes connected by an organic semiconductor containing mobile ions. Aside from the mobile ions, their structure is very similar to that of an organic light-emitting diode (OLED).
Polyethylenimine (PEI) or polyaziridine is a polymer with repeating units composed of the amine group and two carbon aliphatic CH2CH2 spacers. Linear polyethyleneimines contain all secondary amines, in contrast to branched PEIs which contain primary, secondary and tertiary amino groups. Totally branched, dendrimeric forms were also reported. PEI is produced on an industrial scale and finds many applications usually derived from its polycationic character.
Discotic liquid crystals are mesophases formed from disc-shaped molecules known as "discotic mesogens". These phases are often also referred to as columnar phases. Discotic mesogens are typically composed of an aromatic core surrounded by flexible alkyl chains. The aromatic cores allow charge transfer in the stacking direction through the π conjugate systems. The charge transfer allows the discotic liquid crystals to be electrically semiconductive along the stacking direction. Applications have been focusing on using these systems in photovoltaic devices, organic light emitting diodes (OLED), and molecular wires. Discotics have also been suggested for use in compensation films, for LCD displays.
A high-refractive-index polymer (HRIP) is a polymer that has a refractive index greater than 1.50.
Polyfluorene is a polymer with formula (C13H8)n, consisting of fluorene units linked in a linear chain — specifically, at carbon atoms 2 and 7 in the standard fluorene numbering. It can also be described as a chain of benzene rings linked in para positions with an extra methylene bridge connecting every pair of rings.
Andrew Bruce Holmes is an Australian and British senior research chemist and professor at the Bio21 Institute, Melbourne, Australia, and the past President of the Australian Academy of Science. His research interests lie in the synthesis of biologically-active natural products and optoelectronic polymers.
Contorted aromatics or more precisely contorted polycyclic aromatic hydrocarbons are polycyclic aromatic hydrocarbons (PAHs) in which the fused aromatic molecules deviate from the usual planarity.
Eilaf Egap is an Assistant Professor of Materials Science at Rice University. She works on imaging techniques and biomaterials for early diagnostics and drug delivery. She was a Massachusetts Institute of Technology MLK Visiting Scholar in 2011.
Christoph Weder is the Director of the Adolphe Merkle Institute (AMI) at the University of Fribourg, Switzerland, and a Professor of Polymer Chemistry and Materials. He is best known for his work on stimuli-responsive polymers, polymeric materials that change one or more of their properties when exposed to external cues. His research is focused on the development, investigation, and application of functional materials, in particular stimuli-responsive and bio-inspired polymers.
References
- ↑ Heeger, Alan J. (2001). "Semiconducting and Metallic Polymers: The Fourth Generation of Polymeric Materials†". The Journal of Physical Chemistry B. 105 (36): 8475–8491. doi:10.1021/jp011611w. ISSN 1520-6106.
- ↑ Pei, Qibing (2007). "Light-Emitting Polymers". sigmaaldrich.com. SigmaAldrich. Retrieved 1 September 2015.
- ↑ McCullough, Richard D.; Tristram-Nagle, Stephanie; Williams, Shawn P.; Lowe, Renae D.; Jayaraman, Manikandan (1993). "Self-orienting head-to-tail poly(3-alkylthiophenes): new insights on structure-property relationships in conducting polymers". Journal of the American Chemical Society. 115 (11): 4910. doi:10.1021/ja00064a070.