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Organic Field-Effect Transistors for Flexible Electronics Application
Published in Run-Wei Li, Gang Liu, Flexible and Stretchable Electronics, 2019
Jung-Yao Chen, Cheng-Liang Liu
Organic photosensitive material is essential in realizing a flexible photosensitive device. Therefore, the organic photovoltaic material is an appropriate candidate for the charge-transporting material in organic phototransistors. A bulk heterojunction composed of a donor-acceptor system not only provides an effective charge-carrier pathway but also strengthens the photosensitivity through exciton (electron–hole) separation between the junction of donor and acceptor compared to a single component. Photochromic material is a compound that can undergo reversible structural transformations under the influence of light stimuli; this induces a color change, as well as changes in their physical and chemical properties [44]. Through the introduction of photochromic material in the active layer or dielectric layer in an organic phototransistor, the electrical properties can be further verified under light illumination. Besides, the monomer that shows reversible photon-induced polymerization also serves as the photosensitive material in organic phototransistors.
Detectors and Recording Materials
Published in Rajpal S. Sirohi, Optical Methods of Measurement, 2018
Materials that undergo a reversible color change on exposure are called photochromic materials. Photochroism occurs in a variety of materials, both organic and inorganic. Organic photochromics have a limited life and are prone to fatigue. However, organic films of spiropyran derivatives have been used for hologram recording in darkening mode at 633 nm. Inorganic photochromics are either crystals or glasses doped with selected impurities: photochroism is due to a reversible charge transfer between two species of electron traps. Recording in silver halide photochromic glasses has been done in darkening mode at 488 nm and in bleaching mode at 633 nm. Doped crystals of CaF2 and SrO2 have been used in bleaching mode at 633 nm. The sensitivity of photochromics is very low, because the reaction occurs at a molecular level. For the same reason, they are essentially grain-free and have resolution in excess of 3000 lines/mm. Inorganic photochromics have large thicknesses, and hence a number of holograms can be recorded in them. They do not require any processing, and can be reused almost indefinitely. In spite of all these advantages, these materials have limited applications, owing to their low diffraction efficiency (<0.02) and low sensitivity.
SHG of Organic Photochromes in Polymer Matrix: Photo-Assisted Poling and Photo-Switching
Published in Seizo Miyata, Hiroyuki Sasabe, Poled Polymers and their Applications to SHG and EO Devices, 2020
Keitaro Nakatani, Yomen Atassi, Jacques A. Delaire
Polymers as optoelectronic materials are getting widely studied, both from fundamental and practical aspects [1–3]. Contrarily to crystalline systems, these materials can be easily processed as thin films, and introduced as device components. Their relatively low cost is also another advantage. Moreover, the flexibility and the almost limitless possibilities offered by molecular chemistry enable us to build up doped or functionalized molecular-based materials with various properties, making them more competitive. In this respect, our study focuses on polymer matrices combining two different properties, namely nonlinear optical (NLO) properties and photochromism. Photochromic compounds have been studied for many years and are still being thoroughly investigated for their potential applications in glasses, lenses, memories and switching materials [4–8]. Among all external perturbations that yield a molecule’s and material’s property change, those induced by light seem to be worth studying for practical reasons. Light induced NLO property change has been suggested and studied on a molecular scale by Lehn and co-workers [9]. Further-more, as it is well known, the orientation of molecules within the polymer matrix has a large influence on the NLO properties, and the noncentrosymmetry of the material is even a prerequisite to have quadratic NLO effects. Molecular structure change cannot be dissociated from orientational change on a macroscopic scale, and this has been studied by several research groups throughout the world [10,11]. Our study highlights the combination of photochromism and quadratic NLO properties, which leads to two phenomena: on the one hand, photoassisted poling at room temperature in presence of an external electric field; and on the other hand, the photoswitching of NLO properties of a polymer sample.
Synthesis and properties of photochromic polymer contain spiro-oxazine induced by ultraviolet light
Published in Soft Materials, 2023
Cheng-Dong Su, Yi-Yuan Shi, Jun Gao
SO was successfully designed and synthesized before being introduced into PMMA by chemical bonding to improve its thermostability and fatigue resistance. According to the experimental results, the polymerization efficiency was as much as 92.65% when the proportion of SO was 0.4 wt%, which was much higher than we previously reported. Adding plasticizer or polymer soft segment to the polymer system would improve the polymer’s flexibility. With BA content of 50 wt% or DBP content of 20 wt%, the polymer films showed apparent and stable photochromic phenomenon, good thermostability, fatigue resistance, and mechanical properties. Moreover, the polymerization of SO with MMA was triggered by ultraviolet light, with MMA serving as the benign monomer so that no solvent was needed. All monomers were polymerized into a viscous gel that only needed to be imprinted once. The polymerization processes conformed to the concept of green chemistry and were very easy to operate. All things considered, this study provided a new idea for improving the thermostability and fatigue resistance of photochromic materials. The novel photochromic material could be modified for applications in the field of optical information storage, building decoration, protection, and anti-counterfeiting.
Photo-switching behaviour in liquid crystalline materials incorporating a non-planar dithienylcyclopentene core and their birefringence properties
Published in Liquid Crystals, 2022
Hsiuhui Chen, Haochun Yang, Hanwen Kuo, Weiting Ko, Kingo Uchida, Hiroyuki Yoshida
Photochromic materials, which undergo a structural transition upon light absorption such that their colour (i.e. absorbance) changes, are attractive materials from the point of view of optical applications [1]. The colour change is usually associated with a conjugation change in the molecule due to some photoinduced intramolecular cyclisation/cycloreversion. On the other hand, liquid crystals (LCs), typically composed of a rigid planar central moiety and flexible alkyl chains, are materials that exhibit a liquid crystalline phase with long-range molecular ordering within a certain temperature range. For most liquid crystals, the molecules are aligned along an average direction known as the director and show uniaxial anisotropy in various physical properties such as the refractive index, dielectric constant and viscosity. Furthermore, their fluid nature enables the director to be reoriented, leading to advanced materials with properties that can be tuned by external fields.
Experimental analysis of a prototype for a thermochromic Trombe wall
Published in Building Research & Information, 2021
Arturo Martínez, Carmen Alonso, Fernando Martín-Consuegra, Gloria Pérez, Borja Frutos, Álvaro Gutiérrez
Innovative components for solar control have been developed thanks to technological research. When duly activated, so-called dynamic or adaptable materials can reversibly change their thermal-optical properties. Chromogenic (electrochromic, gasochromic, photochromic and thermochromic) glass is the most widespread of those materials (Baetens et al., 2010). In 2015, Reynisson found that a room with an electrochromic window activated in summer saved 10% to 30% more energy than one with adjustable shades and 50% to 75% more than an unprotected opening (Reynisson & Guðmundsson, 2015). One of the strategies suggested by Camacho-Montano to reduce solar gains and hence overheating in school buildings consists in fitting them with electrochromic glass (Camacho-Montano et al., 2020). Thermo-optically variable materials are not limited to glazed elements, however.