CC BY
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11. Komev, N. Complex numerical modeling of dynamics and crashes of wing-in-ground vehicles / N.Komev, K.Matveev // 41st Aerospace Sciences Meeting and Exhibit, 2003
12. Wolf, W.B. de Aerodynamic investigations on a wing in ground effect. A summary of NLR activities in the Seabus-Hydaer programme - NLR-TP-2002-506 / W.B.Wolf. - National Aerospace Laboratory NLR, 2002 - 16 с.
13. Aerodynamics and Optimization of Airfoil Under Ground Effect [Электронный ресурс] / Kyoungwoo Park, Byeong Sam Kim, Juhee Lee, Kwang Soo Kim. // International Journal of Aerospace and Mechanical Engineering 4:3 . 2010 . Системные требования: Adobe Acrobat Reader . URL: www.waset.org/journals/ijame/v4/v4-3-24.pdf (дата обращения: 09.08.2013)
14. Lee, J. Influence of Wing Configurations on Aerodynamic Characteristics of Wings in Ground Effect / Juhee Lee, Chang-suk Han, Chang-Hwan Bae // Journal of Aircraft, Vol. 47, No. 3, 2010 - p. 1030-1040
15.Приходько, А.А. Математическое и экспериментальное моделирование в околоэкранной аэродинамике [Электронный ресурс] : Из доклада на конференции: «Современные проблемы прикладной математики и механики: теория, эксперимент и практика», 24-29 июня 2001 г., Новосибирск / А.А. Приходько, А.В. Сохацкий . Системные требования: Adobe Acrobat Reader . URL: http://www.ict.nsc.ru/ws/NikNik/1486/rep1486.pdf (дата обращения: 09.08.2013)
16. Moore, N. An investigation into wing in ground effect airfoil geometry [Электронный ресурс] / N.Moore, P A.Wilson, A J.Peters // University of Southampton Institutional Research Repository ePrints Soton . 2008 . URL: http://eprints.soton.ac.uk/51083/1/51083.pdf (дата обращения: 09.08.2013)
17. Рисберг, А.Б. Влияние формы крыла на распределение нагрузки по размаху и продольную устойчивость / А.Б.Рисберг. - Москва : ЦАГИ, 1937 - 80 с.
18. Сакорнсин, Р. Аэродинамические характеристики крыла с выступом при разных углах отклонения выступов и различных компоновках крыла гидросамолёта в местах соединения // Электронный журнал «Труды МАИ», № 70.
19. Borst, H.V. Analysis of vehicles with wing operating in ground effect. A collection of technical papers. AIAA/SNAMB Advanced Marine Vehicles Conf. 1979, p. 136-144. Bibl. 18 NN (AIAA Paper X 79-2034)
20.Амплитов, П.А. Влияние геометрических параметров экраноплана типа А на его весовые и экономические характеристики: дис. ... канд. тех. наук : 05.07.02 / Амплитов Павел Андреевич. -Комсомольск-на-Амуре., 2013 - 213 с.
21. Визель, Е.П. Исследование влияния дополнительных консолей на аэродинамические характеристики прямоугольного крыла малого удлинения, движущегося вблизи экрана // Техника воздушного флота №1, 2012 - С. 14-27
22.Антипин, М.А. Анализ несущих поверхностей экранопланов / М.А.Антипин, И.Н.Гусев // Вестник Сибирского государственного аэрокосмического университета им. академика М.Ф.Решетнева № 1 (18), 2008 - С. 101-105
23. Analysis of Two Configurations for a Commercial WIG Craft based on CFD, YANG Zhigang, YANG Wei, LI Yulong, A collection of technical papers 27th AIAA Applied Aerodynamics Conference 2009 (AIAA 2009-4112)
© Амплитов П.А., 2018
УДК 316.79
Douglas A. Suarez R.
Doctor of Science in Telecommunications Engineering, D.Sc.
E-mail: [email protected]
RESULT OF THE STUDY OF THE PHYSICAL - TECHNICAL PRINCIPLES, FOR THE CREATION OF VISUALIZATION DEVICES WITH ORGANIC ELECTRONIC MATERIALS.
Abstract
In this work were developed the physical and technical principles and basis for the creation of display devices
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out of organic electronic materials, as well as stressing the importance that lies in these definitions for the comprehension of the current status of the organic electronics as a new specialty, apart from the traditional one, that looks to keep up with the demands in the area and to provide solutions according to them.
Prominent experts think that the traditional electronics cannot keep up with the current technological requirements, while the best options in terms of applicability and adaptability are offered by the organic branch. Currently, in terms of scientific investigation and practical developments, there is a trend focused on multiplying the efforts dedicated to discover new organic materials with electronic applications, as well as bringing out new techniques in order to improve the use and performance of the devices based on those materials.
The main issue that rises among the disciplines that deal with the organic electronics is the prevalent theoretical insufficiency, considering the importance that theory takes for any scientific approach in order to conceive and concrete any method for practical use. In other words, the current issues concerning the practical scope of the organic electronics are going to be difficult to solve due to the absence of an adequate and strict theoretical frame that precedes the practical implementation of physical and mathematical models. This means that, at the current level of development of the studies regarding the aforementioned principles, the practical use of organic materials could be carried out discretionally and with high probabilities of failure. This involves a challenge for the scientific community in order to further develop the studies about the electronic properties of the organic materials for the purpose of constituting a unified theoretical frame that totally describes the organic electronic processes in conductive materials, polymeric semiconductors and dielectrics.
The last goal after the improvement of the technologies for the development of organic electronics consists on setting it for its practical application in production of devices, which not only would increase the availability of finished products, but also would allow a significant reduction of the price of organic components as well as the substantial simplification of experimental efforts dedicated to the search for adequate materials for technological development, in addition to facilitate the compilation of a real statistic database.
Key words:
organic electronics, visualization devices, organic electroluminescence, physical and mathematical model, conductive materials, polymer semiconductors and dielectrics.
Despite the vast experience in the field of the successful implementation of the electronic devices, it is necessary to master physics in certain kind of processes, especially within the scope of the electrical conductivity, in order to reach the fullest potential in terms of use of organic electronic materials. Most of the attempts to interpret and generalize the conductivity patterns starting only from their molecular structure, have failed. Until now, the fundamental aspects related to the electric properties of the organic materials have been poorly studied, in particular the mechanisms of generation and transport of charge carriers, as well as the impurities' mechanisms that influence on such processes [1].
Nevertheless, the organic electronics is an interdisciplinary field of study that is not fully constituted; so, because of its short period of existence, is not surprising the incipient nature of such theoretical basis. Thus, it is worth to mention the surprising success at practical level that has meant the introduction of this technology in industrial production, a fast advance in this field compared to silicon and germanium based electronics. However, this would be one of the reasons behind the stagnation of theoretical investigation in this area. Given the availability of a great variety of materials for the investigation, the successful attempts directed to the implementation of organic electronic devices promote further investigations destined to the synthesis of new compounds, the modification of those with verifiable margin of success, as well as for the verification of certain important parameters related to the use of those materials, such as to corroborate, that the electrical mobility or the quantum yield does not locate below a given value. The next phase corresponding to those studies consists on the approval, which is given after the creation, at laboratory level, of model devices, which is followed by a deferment of the experimentation and other studies about the materials aforementioned for an indefinite period, or just the discard of continuity from the beginning [2]. As a result, a great volume of experimental data is available, which is related to various types of organic electronic materials; but, on the other side, most of the information responds to a characterization obtained
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from a single perspective that takes into consideration only the materials that are immediately under analysis: there are practically no integrated studies about conductive organic materials and semiconductors. For instance, there is a great amount of previously discussed experiments dedicated to the study of conductivity, in which, in certain circumstances, measurements about current-voltage and lux-amperage were carried out separately, while, in other cases, simultaneous registers were made regarding different processes related to generation and charge transfer. Even so, it has not been possible to elaborate a complete theoretical framework despite the reproducibility of such amount of information. In consequence, there are available different models about the processes of generation and transport of electrical charge in organic semiconductors, each one of them representing, to greater or lesser extent, the regularities associated to such phenomena regarding certain type of material, although it has not been possible to generalize them [3].
For instance, it is known that the prevalent mechanism for charge transfer within a crystal depends on the nature of the interactions based on electronic exchange, between electrons and phonons. In organic semiconductors, such electronic exchange results to be weaker, while the intensity of the interactions between electrons and phonons could be practically the same. This means that this last time of interaction can play a preponderant role concerning the organic semiconductors. Any attempts aimed to the constitution of a band model according to the aforementioned postulates have partially failed: the length of the free path in the order of the reticular constant results to be too low compared to the conventional semiconductors, which is added to the low mobility of the charge carriers, leading to discard any consideration regarding a coherent charge transfer. In order to apply the band model, it is also required that the value equivalent to the band gap exceeds the vibrational energy of the grid. However, the band model adapted to the crystalline organic semiconductors explains effectively phenomena such as the anisotropy of the conductivity and charge mobility, the dependence of this last factor to temperature and the Hall Effect [4].
The tunnel model of the transportation of electrons in organic semiconductors makes possible both the prediction of the carriers' mobility and to explain the compensation effect, as well as the anisotropy of the conductivity, though it does not offer any explanation regarding the negative temperature coefficient of charge mobility and the difference between electron mobility and electron holes [5].
Not all of the conductivity models in semiconductors use the electrons and the holes as charge carriers, due to alternative considerations in which it is quasiparticles the ones acting in the process of current transfer, such as polarons or solitons according to the model to which they respond. Nevertheless, even in such an important topic as the one concerning this text, there are no unified criteria [6].
Additionally, for each type of potential charge carrier, there are two transport mechanisms, which are the constitution of tunnels between equivalent localized states, as wells as the jump between two non-equivalent localized states, during which phonons are emitted and also absorbed [7].
From a perspective that compares the theoretical developments with the experimental results, it could be concluded that, during the process of charge transportation in organic semiconductors at low temperatures, the predominant role will be played by the conductivity according to the band model, while more conductivity will be the result of the action of a jump mechanism. Besides, it could be assumed that, for the majority of the crystals out of organic substances, the electronic transfer at room temperature has an intermediate nature between transmissions based, on one side, on the band model, and on the other side, performed according the jump model of low radius [8].
Even though it is taken for certain, that the conductivity of the organic electronic mat erials has an activating nature, there is not a complete comprehension about the dependence patterns of the activation energy on factors of most importance in the field of electronics, such as temperature and electric field [9].
Everything that was mentioned previously refers to an extant great gap between the information of theoretical nature, which is necessary for the scientific approaches that lead to the elaboration of models, and the constitution of methods for the practical use of the organic electronic materials. In other words, the difficult resolution of problems that exist in the present in the field of organic electronics is going to involve a scientific approach that leads to the concretion of certain tasks according to a rigorous theory. This means, that at the current level of development of the studies of the physical basis for the organic electronics, the practical use of such type of materials
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would come with a considerable margin of error. However, the simplicity that involves obtaining them and the variability of their properties play important roles in favor of the application of organic compounds in electronics [10].
Concerning the application of the principles for the creation and improvement of display devices based on organic electronic materials, it is necessary in first place to determine the parameters that are looked for in the final devices, and then to select those materials that, because of their behavior, are appropriate for such systems [11].
In order to achieve high rates of performance, it is necessary to board a series of technological issues that still remain unsolved due to the current level of development of the production techniques in this area. First, such problems are related to the dynamic of heat release by semiconductor materials during their operation. In order to create high speed devices, it is necessary to use a great number of layers of the organic material, which results to be problematic within the context of searching for constructive solutions due to the poor thermal conductivity of polymers [12].
The work efficiency and lifespan of the displays based on organic materials are determined by the properties of the materials that constitute them. However, a reflection about the distribution and width of the active films that are present in multi-layered structures cannot be omitted. On the basis of such conditions, as it was mentioned previously, there are three (3) tasks destined to the optimization of displays based on organic electronic materials:
1. Make way for the injection of charges from the electrodes to the organic-constituted layers, due to the reduction of the potential barrier for the electrons and holes.
2. To ensure the equilibrium between the charge carriers that make their way into the emission layer.
3. Location of the area for the recombination of electrons and holes (area of excitation) in the emissive layer.
The first two issued are solved by introducing additional layers between the electrodes and the luminophore.
However, it is important to be cautious with this decision: the less the number of working layers are, the higher is going to be the effect that the additional layers will have on the operational parameters of the final device. With this in mind, it could be employed an alternative method for the optimization of the simplest structures consisting of one or two layers: to change the material that constitutes the electrodes in order to allow the reduction of the potential barrier without weakening other operative conditions [13, 23].
The third problem regarding optimization is the most difficult one in absence of a physical and strict scope that encompasses the processes of generation and transmission of excitation. Nevertheless, in many cases, such a problem can be solved through the insertion of additional layers with electronic properties that respond to the place of application. Additionally, it is also possible to discard the emergence of excimers by the replacement of one of the elements taking part in the unwanted reaction with a more suitable material, although finding it is not an easy task. Besides, there are some known methods dedicated to the practical application of a 'non-successful' combination of active layers, such as in already developed devices, in which the excimers or their combination with a luminophore are sources of luminescence. In this case, the optimization of cells is based on the selection of materials for the interface layers, which are in full capacity to form easily intermolecular complexes at that point [14].
Another way to increase the efficiency of the organic light emitting devices, which has proven to be effective in many experiments, is the placement of a luminophore in a matrix which has, on one side, good transportation properties of charge carriers, and, on the other one, allows the reduction of the potential barriers when the charges are moved to the orbitals of emitting molecules HOMO and LUMO. In practically all the instances, the band gap of the material that works as matrix should be wider than that of the guest or emitting substance. In sum, the dilution of the luminophore with another substance eliminates the auto-extinction effect that reduces the brightness of the emission.
Another task, which requires a solution in the context of improving the conditions for visualizing information in multi-layered devices based on organic materials, is the minimization of external quantum efficiency losses due to internal reflection, which can escalate up to the 80% of the generated radiation [15].
Currently, among the constructive methods aimed to the resolution of this problem, it results more appealing the selection of a substrate material with a refractive index lower than the glass, as well as the use of a thick layer for the electronic transportation in order to remove the emitting area of the cathode, so that the light absorption by
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the cathodic material is reduced. The reason behind is that it is not necessary the disposal of a complex design, thus it does not apply either to the manufacturing technology of the product [16, 22].
Among the alternative methods aimed to the elimination of the internal reflection are:
• The use of micro-resonators, which improves significantly the quality of the light emission although, at the same time, is expensive.
• Adding an ultra-thin layer composed of substances with a low refraction level, which should be applied to the external side of the glass substrate, thus allowing the duplication of luminosity although leading to complications in terms of production technologies.
• The application of silicon micro-lenses or micro-spheres on the external side of the glass substrate with the aim of intensifying the radiation dispersion, which derives also in a complex design and in the increase of the cost of the materials destined to the final device.
The short service life of the light-emitting components under operative conditions is one of the fundamental issues regarding the use of organic materials in displays, a fact that inhibits significantly the production on a large scale of organic technologies. As already observed in practice with organic light emitting devices (OLEDs), even during the most successful tests regarding their technical characteristics, the performance indicators decrease gradually, which includes a decline in brightness chromatic distortion, and changes in the voltaic operative indicators and amperage. Evidently, any changes in the characteristics of the device happen during their idle state; however, their deterioration results to be exponentially accelerated because of the electric supply. As mentioned previously, there are already defined three wearing mechanisms for the OLEDs, which are the emergence of black spots on the luminous surface, electric failures and internal degradation, responding the last one mentioned to the progressive decrease of brightness and chromatic alterations in the emissions [17, 21].
The solution to such problems happens to be, in first place, the employment of functional, high purity materials, improved technologies for the assembly of multi-layered structures that completely eliminate, or substantially diminish, the formation of new internal defects; secondly, the isolation of the active layers and electrodes from the environment (encapsulation). To this date, new isolating technologies have been developed, so the problem related to the influence of external factors on the organic elements of the display devices could be considered already solved, in contrast to the work of minimizing the number of defects at internal level of the active materials per se during their production and assembly into multi-layered structures. Thus, the tasks projected to the future would offer a solution regarding improvement of the technology for the synthesis of high-purity organic materials, as well as to the technological processes for the assembly of multi-layered structures [18].
Another mechanism that eases the degradation of the OLEDs is the infiltration of indium or other indium-tin oxide (ITO) particles to the adjacent organic layers. The most effective ways to fight this problem are the introduction of an additional, ultra-thin layer that separates the ITO from the nearest organic, active elements, or the replacement of the ITO with another and more adequate material to fill the function of a transparent electrode in an OLED. The first method, that usually allows the efficiency increase of the organic diodes, is still less preferable after several reasons, among which one has been already mentioned herein, which responds to the design complexities that result in issues of the same category in terms of technology. The second reason responds to the high cost of the ITO. In sum, according to the perspective of the transition from traditional-scale electronics to miniaturized and flexible versions, the replacement of the ITO becomes a top priority, because the last one lacks the necessary plasticity for products with such characteristics [19].
Among the possible options that are available in order to replace the indium-tin oxide are already tested polymers, materials with a composition based on nanotubes, as well as graphene in the shape of a thin layer. The organic light emitting diodes with replacement polymers for the ITO are inferior to the conventional samples in terms of emission characteristics. However, the laboratory models with electrodes composed by graphene even exceed their predecessors. Among these two types of material, graphene is always more preferable. Compared to composed technologies and nanotubes, the multi-layered graphene is much more practical even in economic terms. Another reason for the selection of graphene, apart from its good performance at optical and electrical level in elaborated diodes, is the possibility of producing transparent LEDs without the aid of vacuum processes [20].
As to the characteristics of the final product, in part this equate to their equivalents based on inorganic
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materials, and, in certain situations, they exceed the performance of the last mentioned even during a moment of development of applications and study of the properties of the organic electronic materials, which implies the existence of flaws in the production processes as well as non-solved issues related to the particularities of the physical processes that emerge in the polymeric and molecular forms of these materials, without omitting their quick deterioration under regular, environmental conditions.
Conclusions and recommendations.
• It has been undertaken a theoretical and analytical study of the extant physical and technical foundations related to the organic electronics, as well as a comparison between the results of the experimental studies with the conceptual models of those mechanisms, of which depend the electronic processes in organic semiconductors. It has been established that currently there are many theories related to the charge transfer in organic materials although some of their descriptions, including those related to electronic properties of organic materials, are yet to complete. It has not been omitted the fact that not only the electrons and holes can be considered charge carriers, but also quasi-particles, such as polarons and solitons, and, for each type of carrier, there are variations regarding the transportation models.
• It has been also studied and analyzed the technological properties and elaboration methods of the organic, electronic materials, concluding that the technical characteristics of the current display models equate, and in occasions surpass, the properties of their traditional analogues. At the same time, it has been determined those requirements to be fulfilled by the organic electronic materials in order to integrate them as constituent elements of a multilayered structure.
• It has been schematized the advantages and disadvantages of the use of organic electronic materials, as well as further prospects for the development and use of display devices. At the same time, it has been indicated that the organic, polymeric materials have a greater potential for use because of their physical properties and technological appliances, as the high anisotropy of their mechanical characteristics, their low specific gravity, their solubility, the simplicity of their processing and chemical inertia. The author states that the use of organic, electronic materials provides new prospects about a significant expansion of the functionality of the electronic systems, as wells as a higher integration of them to modern life.
• Leading complex studies about organic semiconductor materials allows to obtain information regarding luminescent, spectral and electronic characteristics under different operative conditions, which include the external electric field, temperature, intensity of the irradiation, among others. The best use that could be given to such studies lies in the generation of new theoretical material, for they provide the biggest amount of information related to individual phenomena and processes, as well as data related to the interaction of the latter.
• It must be stimulated the theoretical studies about the electronic processes in organic semiconductors, mainly in the following areas: the study of the molecular organization of organic electronic materials; the analysis of the energy spectrum and the mechanisms for the excitation, generation and storage of charge carriers; the examination of the systems dedicated to the charge transfer in organic semiconductors, be it different samples of the same origin and between organic and inorganic materials; the observation of the dependency shown by optic or electric properties of the organic semiconductors from temperature, the effects caused by the presence of an external electric field and both the intensity and nature of any type of irradiation.
• Systematizing and organizing the available information about the organic semiconductor materials with a predetermined or potential use; a compilation that would be useful for the creation of a handbook about this type of materials that includes the necessary data related to the electro-optical, chemical and physical properties of them, providing as well information about new samples.
The following methodological, organizational and functional recommendations are provided in order to solve, totally or partially, the issues related to the organic electronics and the concrete use of the aforementioned materials at productive level:
• Promotion of theoretical studies about the electronic processes of the organic semiconductors with emphasis in the following areas:
A. The analysis of the molecular organization of the organic electronic materials.
B. The study of the energy spectrum, mechanisms for the excitation, generation and storage of charge carriers
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in organic semiconductors.
C. An examination of mechanisms for the charge transfer at internal level of a sample out of an organic, semiconductor material as wells as from different samples of the same organic composition or both inorganic and organic.
D. To submit to consideration, the dependence of the electro-optical characteristics of the organic materials from temperature.
E. To analyze the dependence of the aforementioned properties from an external, electric field.
F. To meditate about the alterations that could emerge due to the dependence of the electro-optical properties of organic semiconductors from external irradiations.
Solving these theoretical issues would give answers to the following practical tasks related to the use of organic, electronic materials in the field of information display devices:
1. Extension of the service life of the active materials under operative conditions by means of the elimination or reduction of the presence of excimers.
2. An effective selection of the most adequate solvents for the application of active materials from an active solution without falling into a mutual dissolution o, at least, taking this phenomenon to its minimal expression in terms of affecting the components of the adjacent layers in order to promote the good performance of the functional materials.
3. The proper selection of the switching elements for organic circuits form precise calculations related to the contact phenomena, which also would allow the migration from the use of expensive materials as the ITO to graphene or composites based on nanotubes.
4. The improvement of the methods dedicated to the control of the electro-optical properties of the organic semiconductors through a more precise understanding of the mechanisms for charge transfer as result of the direct amplification of the multi-layered structures' intrinsic conductivity, as well as the reduction of the number of active layers through the elimination of those dedicated to either the conduction or injection of charges.
5. The improvement of the quantum yield of the luminescence proper to LEDs and organic transistors. Bibliographies consulted.
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© Suârez D.A., 2018.
УДК 67.05
А.Д.Ключко
студент, Казанский федеральный университет, г. Набережные челны, РТ E-mail: [email protected] Г.А. Гареева к.п.н., доцент, Казанский федеральный университет, г. Набережные челны, РТ E-mail: [email protected] Д.Р. Григорьева к.п.н., доцент, Казанский федеральный университет, г. Набережные челны, РТ
ОПТИМИЗАЦИЯ ЛИТЕЙНОГО ПРОИЗВОДСТВА ПРИ ПОМОЩИ АДДИТИВНЫХ ТЕХНОЛОГИЙ
Аннотация
В данной статье рассматривается литьевое производство путём его модернизации и оптимизации при помощи аддитивных технологий песочного выращивания.
Ключевые слова
Аддитивные технологии, 3D-принтер, промышленность, литейное производство, традиционное литье,
оптимизация, модернизация.
