[ Instrument network instrument research and development ] Recently, Zhang Fapei's research team from the High Magnetic Field Science Center of Hefei Institute of Material Science, Chinese Academy of Sciences proposed a new strategy for the growth of organic materials induced by a strong magnetic field to achieve structural control of high-performance semiconductor polymer films and improve their charge transport capabilities. Related research results were published on ACS Applied Materials & Interface, Journal of Materials Chemistry C and Applied Physics Letters.
Effective control of molecular orientation and film order in organic semiconductor films is conducive to the realization of high-performance organic field-effect transistors (OFETs) and solar cells. The development of high-efficiency and high-universal solution phase film formation technology is an important way to achieve this goal. The use of a magnetic field to induce the molecular orientation of the film on the macro-scale can be used as a direct and "clean" method to grow large-area oriented organic films, which has attracted the attention of the academic community. In previous research, the research group used a solution coating method under a strong magnetic field to realize the control of the structure and carrier transport characteristics of multiple crystalline (and semi-crystalline) semiconductor polymer films for the first time, and proposed the magnetic orientation of the film. Growth mechanism (Adv. Funct. Mater. 2015, 25, 5126). However, the organic film prepared by this method has problems such as poor morphology and thickness uniformity, uncontrollable film thickness, etc., which affect the repeatability of the photoelectric performance of the film device.
In response to the above problems, Zhang Fapei's research team proposed for the first time a new strategy of solvent vapor annealing (SVA-HMF) under a strong magnetic field. Researchers deposited a "wet film" with uniform thickness by solution spin coating, placed it in a closed container containing saturated organic solvents, and "annealed" it under a strong magnetic field to obtain a donor-acceptor (DA) copolymer P (NDI2OD-T2) film has a large area (centimeter scale) and highly oriented film texture. Researchers have found through microstructure characterization that the morphology and thickness uniformity of the prepared polymer film are improved, and the degree of polymer backbone chain orientation and film crystallinity are better than those prepared by solution coating (ACS Appl. Mater. Interfaces 2020 , 12, 29487); by studying the effect of SVA-HMF conditions on the film structure and morphology, the researchers proposed a strong magnetic-induced solvent annealing to control the dynamic mechanism of polymer film structure; through the preparation of OFET devices, it was found that P(NDI2OD- T2) The mobility anisotropy of the device prepared by the oriented film is 102, and its electron mobility is higher than that of the device prepared by the unoriented film by more than one order of magnitude.
In addition, for another DA copolymer PDPP2TBT with a different molecular structure, the SVA-HMF method can also achieve a large area and highly oriented film, which shows that the method has universal applicability in regulating the structure of semiconductor polymer films. The magnetically oriented PDPP2TBT film exhibits a hole mobility as high as 1.56 cm2/Vs (J. Mater. Chem. C 2020, 8, 4477). The researchers measured the carrier mobility at varying temperatures and found that the thermal activation energy EA of carrier jumping in P(NDI2OD-T2) and PDPP2TBT oriented films is lower than that of unoriented films, which is due to the magnetically induced skeleton chain orientation It leads to the formation of a fast intra-chain charge conduction path, which enhances the delocalization of carrier jumping motion. Studies have shown that adding a small amount (2.0wt%) of graphene nanosheets to the semiconductor polymer matrix can further improve the molecular chain orientation of the polymer film prepared by SVA-HMF, and enhance the carrier anisotropy of OFET devices (Appl . Phys. Lett. 2020, 117, 063301).
What is a semiconductor?
Semiconductor refers to a material whose conductivity is between that of a conductor and an insulator at room temperature.
Semiconductors are used in integrated circuits, consumer electronics, communication systems, photovoltaic power generation, lighting, high-power power conversion and other fields. For example, diodes are devices made of semiconductors.
Whether from the perspective of technology or economic development, the importance of semiconductors is very huge. The core units of most electronic products, such as computers or digital recorders, are closely related to semiconductors.
Common semiconductor materials include silicon, germanium, gallium arsenide, etc. Silicon is an influential one in the application of various semiconductor materials.
This research is helpful to deepen the understanding of the interaction mechanism between the magnetic field and organic semiconductor molecules, the relationship between the structure of organic semiconductor thin film and the performance of related devices. The magnetically induced thin film growth method proposed by the research team provides a way to develop new high-performance organic semiconductor materials and improve the photoelectric performance of devices. The research work is supported by the National Natural Science Foundation of China and national key research and development projects.
The application of new semiconductor materials in industry is increasing. New semiconductor materials are characterized by their stable structure, excellent electrical properties, and low cost. They can be widely used in the manufacture of modern electronic equipment. Compared with other countries, my country still has a large gap in this respect. It is manifested in the production and processing of some basic instruments. In recent years, many national departments have targeted my country’s weaknesses relative to other countries. In this regard, various groups have been organized in a unified manner to provide effective leadership. Then work together to develop higher-level semiconductor materials. Only in this way can it adapt to the progress and development of my country's industrialization to a large extent, and provide a stronger driving force for my country's social progress. First of all, it is necessary to further research and develop superlattice quantum well materials. From the current development background of semiconductor materials in China, it is necessary to improve the ultra-high brightness to a large extent. Red, green and blue materials and optical communication materials will be developed in the future. In the main research direction of the company, it must be strengthened according to the requirements of newer generation electronic devices and circuits in the market, and the needs of these optoelectronic structure materials in the future production process will be carefully analyzed and discussed, and then to meet the future world In the direction of semiconductor development, we need to choose a more optimized layout, and then do related development and research work, so that a better communication mechanism between various R&D institutions and enterprises can be achieved to a large extent in high temperature semiconductor materials , Further development and utilization.
Source: Encyclopedia, Hefei Institute of Material Science
Titanium Dioxide(TIO2)
Titanium dioxide is an important inorganic chemical pigment, the main component is titanium dioxide. The production process of titanium dioxide has two process routes: sulfuric acid method and chloride method. It has important applications in coatings, inks, papermaking, plastics and rubber, chemical fiber, ceramics and other industries.
It has two types: rutile type (Rutile R type) and anatase type (Anatase A type). The rutile crystal structure is compact, relatively stable, and has low optical activity, so it has good weather resistance, and has high hiding power and decolorizing power.
Titanium dioxide is widely used in coatings, plastics, rubber, ink, paper, chemical fiber, ceramics, daily chemicals, medicine, food and other industries.
The coating industry is the largest user of titanium dioxide, especially Rutile Titanium Dioxide, most of which is consumed by the coating industry. The paint made of titanium dioxide has bright colors, high hiding power, strong tinting power, low dosage, and many varieties. It can protect the stability of the medium, and can enhance the mechanical strength and adhesion of the paint film to prevent cracks. Prevent the penetration of ultraviolet rays and moisture, and extend the life of the paint film.
The plastics industry is the second largest user. Adding titanium dioxide to plastics can improve the heat resistance, light resistance, and weather resistance of plastic products, improve the physical and chemical properties of plastic products, enhance the mechanical strength of the products, and extend the service life.
The paper industry is the third largest user of titanium dioxide. As a paper filler, it is mainly used in high-grade paper and thin paper. Adding titanium dioxide to the paper can make the paper have better whiteness, good gloss, high strength, thin and smooth, no penetration during printing, and light weight. Titanium dioxide for papermaking generally uses Anatase Titanium Dioxide without surface treatment, which can act as a fluorescent whitening agent and increase the whiteness of paper. However, laminated paper requires the use of surface-treated rutile titanium dioxide to meet the requirements of light resistance and heat resistance.
Titanium dioxide is also an indispensable white pigment in advanced inks. The ink containing titanium dioxide is durable and does not change color, has good surface wettability and is easy to disperse. The titanium dioxide used in the ink industry has rutile type and anatase type.
The textile and chemical fiber industry is another important application field of titanium dioxide. Titanium dioxide for chemical fiber is mainly used as a matting agent. Since the anatase type is softer than the gold red type, the anatase type is generally used. Titanium dioxide for chemical fiber generally does not require surface treatment, but in order to reduce the photochemical effect of titanium dioxide and prevent the fiber from degrading under the action of titanium dioxide photocatalysis, surface treatment is required for some special varieties.
The enamel industry is an important application field of titanium dioxide. The enamel grade titanium dioxide has high purity, good whiteness, fresh color, uniform particle size, strong refractive index and high color reducing power, and has strong turbidity and Opacity, make the coating thin, smooth and strong acid resistance after enamelling. It can be evenly mixed with other materials in the enamel manufacturing process, does not agglomerate, and is easy to melt.
The ceramic industry is also an important application field of titanium dioxide. Ceramic grade titanium dioxide has high purity, uniform particle size, high refractive index, excellent high temperature resistance, and does not change ash at 1200°C for 1 hour. High opacity, thin coating, light weight, widely used in ceramics, construction, decoration and other materials.