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Organic Light-Emitting Devices and Their Applications for Flat-Panel Displays
Published in Zhigang Rick Li, Organic Light-Emitting Materials and Devices, 2017
Conjugated polymers are a novel class of semiconductors that combine the optical and electronic properties of semiconductors with the processing advantages and mechanical properties of polymers. The molecular structures of several popular conjugated polymers are shown in Figure 1.1. Before the revolutionary discovery of conjugated polymers, polymer science and technology had focused on “saturated” polymers, i.e., conventionally nonconductive polymers (a term for macromolecules with repeat structure units). In “saturated” polymers, the valence electrons of the carbon atoms in the main chain are hybridized in sp3 configuration, and each carbon atom is bonded to four other atoms. As a result, the electronic orbitals are fully saturated. Owing to their electronic structures, saturated polymers have wide energy gaps and are electrically insulating.
Introduction to Techniques and Instrumentation
Published in Bernard Fried, Joseph Sherma, Practical Thin-Layer Chromatography, 2017
Cserháti Tibor, Forgács Esther
Colored substances can be visually detected on the plates. However, the majority of solutes do not absorb in the visible part of the spectrum, and these solutes have to be detected by other means. Many organic compounds contain one or more conjugated electron systems that absorb light in the ultraviolet (UV) part of the spectrum. These solutes can be easily detected on plates containing one or more fluorescent indicators. These indicators can be excited by UV light (usually 254 nm) and they emit visible radiations. Solutes with absorbing capacity in the UV region absorb the radiation and are detected as dark spots on a green or pale blue background (fluorescence quenching). Some solutes have the capacity to emit fluorescent light when excited with UV light. The detection of these solutes is easier on nonfluorescent layers. Commercial UV lamps emitting about 365 nm can often be successfully used for the detection. As the number of fluorescent compounds is relatively low, this method offers a unique possibility for the sensitive detection of solutes present in complicated nonfluorescent matrices. Impregnating plates containing fluorescent solutes with paraffin oil or with polyethylene glycol increases the stability of fluorescence. An interesting possibility for the documentation and evaluation of TLC results is the image analysis of photochemically derivatized solutes.73
An Insight into the Synthesis and Optoelectronic Properties of Thiophene-2,4,6-Triaryl Pyridine-Based D-A-D Type π-Conjugated Functional Materials
Published in Anandhan Srinivasan, Selvakumar Murugesan, Arunjunai Raj Mahendran, Progress in Polymer Research for Biomedical, Energy and Specialty Applications, 2023
Unlike the synthesis of inorganic materials, which are mostly brittle and hard, and usually involves high temperatures (T ≥ 500°C) (Pell et al., 2004), the conjugated materials are mechanically flexible in nature and can be easily synthesized through robust, cost-effective organic reactions such as condensation reactions, green synthesis, one-pot multicomponent reactions, palladium-catalyzed cross-coupling reactions, and so on (Y.-J. Cheng et al., 2009; Demeter et al., 2014). The modern organic synthetic methods allow facile functionalization of the conjugated systems which can readily tune their photophysical and electronic properties, making the conjugated materials a mainstay of our technological existence (Forrest, 2004; Gibson et al., 2012).
Molecular simulation of liquid crystals
Published in Molecular Physics, 2019
The electronic properties of conjugated π-systems have proven useful in the development of a range of technological devices, including solar cells and light emitting diodes. Liquid crystalline systems offer the possibility of combining orientational order with ease of processing and self healing. In particular, disk-like molecules consisting of an extended aromatic core with attached flexible aliphatic side chains may form Col phases with interesting electronic properties. To investigate these in a simulation, a combination of at least three computational techniques is typically needed: (i) molecular electronic structure is computed via quantum chemistry; (ii) atomic level md is carried out, typically of a few hundred molecules, to obtain the global and local arrangement of molecules in the mesophase; (iii) a kinetic mc simulation model of charge transport is constructed, based on the information obtained from the md. There is the possibility of using cg models for the md, but this carries some dangers, since the charge-transport will be quite sensitive to details of both structure and dynamics.
Carrier transport and device applications of the organic semiconductor based on liquid crystalline non-peripheral octaalkyl phthalocyanine
Published in Liquid Crystals, 2018
Masanori Ozaki, Makoto Yoneya, Yo Shimizu, Akihiko Fujii
Since molecules and polymers having an extended π-conjugated system have excellent electronic and optical characteristics as a semiconductor, active research and development have been promoted for applications to light emitting devices, transistors, solar cells, and so on. However, molecules with extended π-conjugated planes such as pentacene and phthalocyanine (Pc) are insoluble due to strong intermolecular interaction. Likewise, π-conjugated polymers such as polyacetylene and polythiophene can not be also dissolved in any solvent and do not melt even by heating up to decomposition temperature. These properties were problem in terms of processability to the device. In the latter half of the 1980s, by introducing flexible side chains into a π-conjugated rigid main chain, conducting polymers soluble in common solvents and excellent in film formability were developed and the way for printable electronics was opened [1–3]. Furthermore, even in π-conjugated small molecules, soluble organic semiconductors have been developed upon the introduction of side chains to rigid core, and the development of printable devices is progressing [4,5]. It should be noted here that such an approach for solubilisation of organic semiconductors is the same as a strategy for designing liquid crystalline molecules. In addition, since liquid crystals have self-organisation properties, liquid crystalline semiconductors are very attractive for realising organic electronic devices which require molecular arrangement control over a large area [6–16].