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Jan 4 2018

Detailed Annotation of Organic Semiconductor

Warm hints: The word in this article is about 3000 and reading time is about 15 minutes.

Summary
Organic semiconductors are organic materials with semiconducting properties. They are organic compounds with thermal conductivity and electrical conductivity ranging from 10-10 to 100S. Cm-1, between conductive metals and insulators. Organic semiconductors can be divided into three types: organic matter, polymer and donor - receptor complex. This article is talking about organic semiconductor in great detail including its advantages and disadvantages,conductive mechanism,research and development and ect.


Article Core

Organic semiconductorFeaturessmall organic molecules
English nameOrganic semiconductors

Category

chemical industry




Catalogs

catalogs

I.concepts and properties

4.2 Electronic (n type) organic semiconductors

5.4 organic sensors

 

II.Advantages and disadvantages

V.research status and development trend

5.5 Integrated intelligent systems

 

III.history of research

5.1 Organic solar cells(OSC)

六VI.Preparation and processing

IV.conductive mechanism

5.2 Organic Light-Emitting Diode, (OLED)


4.1 Hole type (P type) organic semiconductors

5.3 RFID tags






Introduction

I.concepts and properties

Organic semiconductors are organic materials with semiconducting properties. They are organic compounds with thermal conductivity and electrical conductivity ranging from 10-10 to 100S. Cm-1, between conductive metals and insulators.

It  is mainly a class of small organic molecules and polymers containing TT conjugated structures. Before we begin to read the following article,let's see a video at first: 

This video provides an intuitive description of the organic semiconductors from

materials, production and development. After this video,let's enter into the subject.

II.Advantages and disadvantages

Advantages

  • 1.soft,large area (soft screen)

  • 2. preparation is simple (without high vacuum, high temperature)

  • 3. optoelectronic (conductive, transparent, luminescent)

  • 4. molecular device

  • 5.Diversity and variability of molecular structure (material design)

Disadvantages

  • A.Device life and stability and so on need to be studied and improved

  • B.Application areas need to be further expanded

III.history of research

  • In 1954, Japanese scientists Akamatsu and wellhead found that the Cl doped aromatic carbohydrate thin film produced current and conductivity of 0.1S/cm, so the concept of organic semiconductor was first put forward.

  • In 1974,The first polymerization of polyacetylene film (insulation) by Japanese scientist Shirakawa Hideki et al.

  • In 1977,Hagrid, Mark Diarmuid, and Shirakawa Hideki, and others, make the polyacetylene film a good conductor by doping, thus producing a conductive polymer that is comparable to that of copper.

  • In 1986,Tsumura and others used polythiophene organic semiconductors for the first time as active layers to prepare OFET. The carrier mobility of the device at that time was very low, but it uncovered the upsurge of research on OFET.

  • In 1987,American Kodak research laboratory C.W.Tang (Chinese American scientist Dr. Deng Qingyun) and other organic light-emitting diodes (OLED) are used for organic light-emitting diodes (OLED)

  • In 1990,J.H.Burroughes, Cavendish Laboratory of University of Cambridge, published articles on NATURE. They reported that they developed polymer light-emitting diodes (polymers).

  • In 1997, People gradually shift the research focus to the morphological structure control, interface state, and device integration of organic semiconductors.

  • In 2000,Bell labs J.H.Schon (Schoen) and others reported on Nature that they used self-assembled monolayers to prepare organic molecular field-effect transistors, and promoted the new progress of molecular electronics. They were selected as one of the ten greatest achievements in science and technology in the year.

  • In 2003,The J. Kalinowski team reported the magnetic effect of organic light emitting devices for the first time

  • In 2011,Japanese researchers used an ink containing organic semiconductor C8BTBT and for promoting the crystallization of the organic semiconductor ink, successively spraying, solves the problem of uneven coating of semiconductor

  • ... The future is full of infinite possibilities





Detail

IV.conductive mechanism

Type P hybrids: [CH]n + 3x/2 I2 to [CH]nx+ + xI3-

N type hybrids: [CH]n + xNa, [CH]nx- + xI3-

The experiment shows that in organic polymers, doping leads to a rapid rise in electrical conductivity, and at the same time, the magnetic susceptibility is almost 0 in a considerable range. This shows that the carrier that causes the electrical conductivity to rise is not the electrons and holes in the general conductor or the semiconductor.

conductive mechanism--Detailed Annotation of Organic Semiconductor


If ordered, large molecules -- > amorphous structure -- > low carrier mobility5. research status and development trend

The degree of order of amorphous structure is different, which leads to different energy levels of molecules, which will form different order of energy levels similar to the band structure of crystalline materials. Usually, the LUMO level of organic semiconductor materials with certain energy gap is usually opposite to the conduction band bottom level of traditional semiconductors, and the HOMO level is opposite to the top level of the valence band of traditional semiconductor.

Because the energy gap of organic semiconductor materials can be stabilized, that is, the energy difference between LUMO and HOMO is usually large, and the electron affinity is low. Most organic semiconductor materials are p type, that is, most materials can only transmit positive charges. This positive charge represents the oxidation state of an organic molecule that loses an electron (usually an electron at the HOMO level).

4.1 Hole type (P type) organic semiconductors

(HOMO energy level is lower, electron ionization potential is larger, it is beneficial to receive the cavity of injection).

Structural features

  • 1.The molecule has a large PI conjugate and a p- PI conjugate orbit with a charge transfer task.

  • 2.The molecule contains N atoms that can provide P electrons, usually aromatic amines, and the aromatic rings contain electronic groups.

  • 3.Small molecular crystals with a molecular weight less than 1000 have certain vitrification temperature and clear melting point.

Types

Include hydrazone, three aniline, butadiene styrene based three aniline and so on.

Hole type (P type) organic semiconductors--Detailed Annotation of Organic Semiconductor


4.2 Electronic (n type) organic semiconductors

(LUMO higher energy level, smaller electron affinity potential, favorable for receiving injected electrons.)

Structural features

Aromatic rings have electron absorption groups, such as oxygen atoms, nitro groups, amides, metal ions and so on.

Types

Aromatic compounds

Electronic (n type) organic semiconductors--Detailed Annotation of Organic Semiconductor

V.research status and development trend

Since the late 1990s and early 2000s,the research of organic semiconductor materials has attracted great attention in related fields,which dramaticly improved the fabrication level of organic semiconductor devices in laboratory environments.Currently,the field of organic semiconductor devices is entering commercial phase.

Detailed Annotation of Organic Semiconductor

Several types of active and passive devices have been made available at present,such as transistor, diode, OLED, sensors, memory, display, battery, resistor, capacitor, Inductor and antenna,etc.

5.1 Organic solar cells(OSC)

Organic solar cells, as the name implies, are the solar cells that make up the core parts of organic materials. The main purpose is to use the photosensitive organic matter as the material of the semiconductor, and generate the current by the photovoltaic effect, so as to achieve the effect of solar power generation.

Solar cells mainly include two kinds of crystalline silicon batteries and thin film batteries. Their respective characteristics decide that they have an irreplaceable position in different applications. However, the next 10 years, crystal silicon solar battery share despite decreased due to thin film solar cell development and other reasons, but the dominant position is still not fundamentally changed; and if the thin film battery can solve the conversion efficiency is not high, the preparation of thin film batteries for expensive equipment and other issues, will have a huge space for development.

Organic solar cells(OSC)--Detailed Annotation of Organic Semiconductor

Structure principle of OSC include the following states

  • 1.Organic solar cells use the photosensitive organic matter as the material of the semiconductor, and generate the current by the photovoltaic effect. The main photosensitive organic materials have conjugated structures and have electrical conductivity, such as phthalocyanines, porphyrins, and Cyanines (cyanine).

  • 2.The organic solar cells can be divided into a single junction structure, a P-N heterojunction structure and a dye sensitized nanocrystalline structure according to the semiconductor materials.

  • 3.The structure of the single junction is an organic solar cell based on the principle of Schotty barrier. The structure is glass / metal electrode / dyestuff / metal electrode. The electric field of two electrodes can generate an electric field. The electrons are transferred from the metal electrode of the low power function to the high power electrode, resulting in the photocurrent. As the electron hole is transmitted in the same material, the photoelectric conversion rate is low.

  • 4.The structure of p-N heterostructure refers to the structure of the heterostructure with the donor receptor (N type semiconductor and P type semiconductor), and the structure of the heterostructure. The semiconductor material for dyes, such as phthalocyanine and perylene four formaldehyde imine compounds, using the semiconductor layer between the D/A interface (Donor, Acceptor, donor, receptor) properties and electron hole transfer respectively in different materials, the separation efficiency is improved. Elias Stathatos and others combine the advantages of inorganic and organic compounds to make the photoelectric conversion of solar cells in 5%~6%.

  • 5.ye sensitized solar cells (DSSC) mainly refer to a type of solar cell with a dye sensitized multi space nanostructured TiO2 film as a photo anode. It is a solar cell with the principle of chlorophyll photosynthesis of the bionic plant. However, NPC solar cells can use appropriate redox electrolyte to improve the photoelectric efficiency, and generally stabilize 10%. Moreover, the preparation of nanocrystalline TiO2 is simple, low-cost, and life expectancy. It has good market prospects.

5.2 Organic Light-Emitting Diode, (OLED)

Organic light-emitting diodes (OLED) are also called electromechanical laser displays and organic light-emitting diodes. Deng Qingyun (Ching W. Tang), a Chinese American professor, was found in the laboratory in 1979. OLED display technology has the advantages of self luminescence, wide angle of view, almost infinite high contrast, low power consumption, high reaction speed and so on.

Organic Light-Emitting Diode, (OLED)--Detailed Annotation of Organic Semiconductor

OLED display technology is widely used in mobile phones, digital cameras, DVD, personal digital assistants (PDA), notebook computers, car audio and TV. The OLED display is very thin and light because it does not use the backlight. The OLED display also has a wide screen view of a maximum of 160 degrees, with a operating voltage of two to ten volts (volt, expressed in V).

OLED display technology has the characteristics of self luminous, the coating of organic material and the glass substrate is very thin, when a current is passed, these organic materials will be light, and OLED display screen viewing angle, and can save energy, from the beginning of 2003 the display device has been applied in a MP3 player.

5.3 RFID tags

Radio frequency identification (RFID) is a wireless communication technology. It can identify specific targets through radio signals, read and write related data, and do not need to identify mechanical or optical contact between the system and specific targets.

The radio signal is transmitted through the electromagnetic field modulated by radio frequency to transmit data from the tag attached to the object, so as to automatically identify and track the item. Some tags can get energy from the electromagnetic fields emitted by the recognizer when they are recognized, and do not need batteries. They also have labels, which own power, and can send out radio waves (radio frequency electromagnetic fields). The label contains electronic information stored within several meters can be identified. Unlike barcodes, RFID tags do not need to be within the line of sight of the identifier and can be embedded in the tracked objects.

RFID technology is used in many industries. Attaching the label to a car in production, the factory is convenient to track the car's progress on the production line. The warehouse can track the location of the drug. RFID tags can also be attached to livestock and pets, making it easy to identify livestock and pets. Radio frequency identification card enables employees to enter the locked part of the building, and the radio responder on the car can also be used to collect fees and parking lots.

RFID is one of the ten most influential technologies in this century, however,because of the high costs, this technology didn’t be popularized and developed. The research and development of organic RFID with low costs could solve this problem in the future. At present, the world is still in the exploration stage, but it is generally good for its prospects.

5.4 organic sensors

Organic sensors are sensors that use organic polymer materials as sensitive materials. Organic polymer materials are new materials developed in the 60s. They have electronic, optical, thermal, mechanical, chemical and biological characteristics, and expand the field of sensor technology. The most rapid development of electronic functional polymer materials such as Li Min, thermosensitive and photosensitive components. For example, polyvinylidene fluoride copolymer and its series of materials with excellent radiation resistance, electrical insulation, chemical stability, thermal stability, after stretching, polarization, plating electrode treated processed into thin films, showing strong piezoelectric effect, piezoelectric effect and pyroelectric effect, application prospect in sensor was striking. It has developed a stereo headset, microphone, speaker, high-frequency accelerometer, hydrophone, sonar detectors, marine monitoring device, coast guard device, underwater acoustic imaging, ultrasonic nondestructive testing, surface acoustic wave, delay line, contactless switch, keyboard switch, optical fiber switch, infrared detector, intrusion alarm and printing sensor etc.. In medical devices, there are heart sounds, fetal tone meter, pulse meter, real-time ultrasonic imaging device for human tissue, A ultrasonic scanning equipment, blood flow detector, prosthetic sensor, blind tactile sensor and other products. For example, three glycine sulfate organic thermoluminescent thin film has high pyroelectric coefficient. It is a non-contact new thermoelectric sensitive material, which can directly convert heat radiation into electrical signal. This sensor has high response frequency, fast speed, wide frequency band, and is not limited by radiation wavelength. It has unique advantages in gas analysis, telemetry, remote sensing and so on.

5.5 Integrated intelligent systems

With the development of computer network, communication, artificial intelligence, expert system, intelligent database, multimedia, neural network, genetic algorithm and neural fuzzy theory, intelligent control, robot technology, especially the theory of neural network into the widespread penetration of integrated intelligent system (IIS) has been extensive research and development, IIS is actually a a concrete manifestation of trying to simulate the distance of two individual a few hundred meters through the eyes for remote communication, IIS intelligent man is trying to accomplish these, including intelligent hands and feet, eyes, ears, mouth, reasoning, control, associative memory, intelligent technology is not possible to use these functions in a single to complete, need to use a variety of intelligent technology integration and realize the intelligent complex people. IIS available concrete block description. It includes three parts: reasoning, transfer, action, for the people, part of the complete reasoning by a large number of neurons in the human brain, the reasoning result is transferred to the hands of other organs through all kinds of neural letter 1, action is carried out by the external organs, it sent a complete reasoning command.

Integrated intelligent systems--Detailed Annotation of Organic Semiconductor

Application of IIS including banks, process control and automation, monitoring, robot systems, manufacturing systems, information services, implementation of IIS must use special software development environment: a variety of standard general software development environment, expert system, neural network simulator control and robot system simulator, existing software module, standardization the robot, control and automation module, based on the special use of language, such as for use with parallel inference machine for developing distributed control software development efficiency than FORTRAN, C language is more advanced and high real-time oriented Paracell language, concurrent means must also be provided by the hardware (Transputer, OCCAM in concurrent language the giant, and the use of a variety of parallel machines) in the technical drawings.



Analysis

VI.Preparation and processing

Organic Semiconductor Technology has a broaden develop vision in various applications, more and more companies and institutions were involved in the field of development and research of organic semiconductor technology. According to the results of 2009, there are 15 countries over 70 companies in Europe are engaging in organic semiconductor. As the development of technical level of mass manufacturing, organic semiconductor technology will become a practical technology and competitive with inorganic semiconductor technology.The practical level of OLED television has reached a considerable degree, and the market share is increasing. As the cost of manufacturing is greatly reduced, OLED TV will be a necessary household appliance for millions of users. What’s more, OLED technology will be helpful for the development of electronic newspaper.

Preparation and processing--Detailed Annotation of Organic Semiconductor

All in all,after thirty years of development, as new materials for applications in electronics and opto-electronics, organic semiconductors have gone through the stages of material development, basic research and device engineering. At present, organic displays and other devices have entered the stage of commodity speech development, and show attractive prospects for development.

Preparation and processing--Detailed Annotation of Organic Semiconductor

Organic semiconductor devices have many advantages, such as easy processing, low cost, low power consumption and many other inorganic semiconductor devices. However, compared with the in-organic semiconductor devices, organic semiconductor devices need to improve the performance, service life and manufacturing process and etc. At present, organic semiconductor devices still have some technical problems to solve, such as slow speed, so it is unlikely to replace traditional semiconductor devices in the near future to occupy the leading position in the market. However, if the most concerned question is price, not speed or other factors, organic semiconductors are a better choice.

Semiconductors in twenty-first Century will not be limited to silicon based semiconductor technology, organic semiconductor materials and metal oxides, so as to further reduce costs and improve stability and reduce energy consumption.



Book Recommendation

  • Electronic Processes in Organic Semiconductors: An Introduction

The first advanced textbook to provide a useful introduction in a brief, coherent and comprehensive way, with a focus on the fundamentals. After having read this book, students will be prepared to understand any of the many multi-authored books available in this field that discuss a particular aspect in more detail, and should also benefit from any of the textbooks in photochemistry or spectroscopy that concentrate on a particular mechanism.Based on a successful and well-proven lecture course given by one of the authors for many years, the book is clearly structured into four sections: electronic structure of organic semiconductors, charged and excited states in organic semiconductors, electronic and optical properties of organic semiconductors, and fundamentals of organic semiconductor devices.

--Anna Köhler (Author),‎ Heinz Bässler (Author)

  • Physics of Organic Semiconductors

The field of organic electronics has seen a steady growth over the last 15 years. At the same time, our scientific understanding of how to achieve optimum device performance has grown, and this book gives an overview of our present-day knowledge of the physics behind organic semiconductor devices. 

--Wolfgang Brütting (Editor),‎ Chihaya Adachi (Editor)




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