Charge transport in organic semiconductors

2020 ◽  
pp. 171-292
Author(s):  
Stephen R. Forrest
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors ◽  
Photonic Devices ◽  
Basic Principles ◽  
Inorganic Semiconductors ◽  
Charge Densities ◽  
Disordered Films ◽  
Inorganic Semiconductor ◽  
Background Charge ◽  
Almost All

In this chapter, the basic principles of the origins of transport levels and bands, charge conduction in disordered materials, and injection from contacts are introduced. Charge transport in organics is fundamentally different than in inorganic semiconductors due to narrow transport bands that, in general, lead to charge transport via hopping, resulting in carrier mobilities that are at most only a few cm2/V s. Processes of charge injection leading to space charge limited transport that defines the current vs. voltage characteristics of the materials are discussed. Methods of measuring mobility, background charge densities, and quantifying charge recombination are described. Doping of organics using both molecular and atomic species to modify their conductivity is also considered. The theory of transport in energetically and structurally disordered films is developed. The chapter closes by describing, from first principles, the theory of conduction over organic and organic/inorganic semiconductor heterojunctions that are used in almost all organic photonic devices.

scholarly journals Structure prediction of N-heteroacenes as potential organic semiconductors

2014 ◽  
Vol 70 (a1) ◽  
pp. C1621-C1621
Author(s):  
Josh Campbell ◽  
Graeme Day
Keyword(s):  
Solid State ◽  
Charge Transport ◽  
Electronic Properties ◽  
Organic Semiconductors ◽  
Structure Prediction ◽  
Crystal Packing ◽  
Polyaromatic Hydrocarbons ◽  
Ring Structure ◽  
Inorganic Semiconductors ◽  
Nitrogen Substitution

Organic electronics offer exciting new alternatives to traditional inorganic devices based on advantages such as lower cost, ease of manufacture and flexibility. Small molecule semiconductors such as pentacene and rubrene are the focus of intense research due to performance approaching that of inorganic semiconductors. Charge transfer in polyaromatic hydrocarbons (PAHs) relies on the degree of π-conjugation and overlap of the π-systems of neighbouring molecules in the solid state. Small changes in the intermolecular interactions can lead to important changes in crystal packing and electronic properties. Thus, functionalization of PAHs is often used to improve their packing in the solid state. The addition of electronegative atoms into the ring system of pentacene has been proposed for improving stability while retaining attractive properties. [1] N-heteroacenes result from the substitution of nitrogen into the arene ring structure. The resulting potential for weak hydrogen bonding could direct coplanar molecular arrangements, sheet formation and favourable π-overlap for charge transport. Theoretical studies [2] have been carried out showing promising properties at the molecular level. As of yet no analysis of the solid state of these molecules has been performed to investigate how this substitution affects the packing and electronic properties. Here, we present the results of crystal structure prediction studies and calculation of charge transport properties aimed at understanding the influence of nitrogen substitution on the crystal packing of N-heteropentacenes and their performance as semiconducting materials.

Design and Synthesis of Two-Dimensional Covalent Organic Frameworks with Four-Arm Cores: Prediction of Remarkable Ambipolar Charge-Transport Properties

2019 ◽  
Author(s):  
Simil Thomas ◽  
Hong Li ◽  
Raghunath R. Dasari ◽  
Austin Evans ◽  
William Dichtel ◽  
...  
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors ◽  
Density Functional ◽  
Polymer Networks ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
X Ray Diffraction ◽  
Zinc Porphyrin ◽  
Design And Synthesis ◽  
Predicted Values

<p>We have considered three two-dimensional (2D) π-conjugated polymer networks (i.e., covalent organic frameworks, COFs) materials based on pyrene, porphyrin, and zinc-porphyrin cores connected <i>via</i> diacetylenic linkers. Their electronic structures, investigated at the density functional theory global-hybrid level, are indicative of valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular approach to derive the electronic couplings between adjacent core units and the electron-vibration couplings, the three π-conjugated 2D COFs are predicted to have ambipolar charge-transport characteristics with electron and hole mobilities in the range of 65-95 cm<sup>2</sup>V<sup>-1</sup>s<sup>-1</sup>. Such predicted values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, we have synthesized the zinc-porphyrin based 2D COF and carried out structural characterization via powder X-ray diffraction and surface area analysis, which demonstrates the feasability of these electroactive networks.</p>

Rational design and crystal structure prediction of ring-fused double-PDI compounds as n-channel organic semiconductors: a DFT study

2021 ◽  
Author(s):  
Suryakanti Debata ◽  
Smruti R. Sahoo ◽  
Rudranarayan Khatua ◽  
Sridhar Sahu
Keyword(s):  
Crystal Structure ◽  
Charge Transport ◽  
Organic Semiconductors ◽  
Structure Prediction ◽  
Rational Design ◽  
Molecular Design ◽  
Design Strategy ◽  
Dft Study ◽  
Crystal Structure Prediction ◽  
Model Compounds

In this study, we present an effective molecular design strategy to develop the n-type charge transport characteristics in organic semiconductors, using ring-fused double perylene diimides (DPDIs) as the model compounds.

Charge transport in doped organic semiconductors

2003 ◽  
Vol 68 (8) ◽  
Author(s):  
Yulong Shen ◽  
Kenneth Diest ◽  
Man Hoi Wong ◽  
Bing R. Hsieh ◽  
David H. Dunlap ◽  
...  
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors

Charge-Transport in Crystalline Organic Semiconductors with Liquid Crystalline Order.

ChemInform ◽  
2005 ◽  
Vol 36 (44) ◽  
Author(s):  
Panos Vlachos ◽  
Bassam Mansoor ◽  
Matthew P. Aldred ◽  
Mary O'Neill ◽  
Stephen M. Kelly
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors ◽  
Liquid Crystalline ◽  
Crystalline Order

On Razors Edge: Influence of the Source Insulator Edge on the Charge Transport of Vertical Organic Field Effect Transistors

MRS Advances ◽  
2017 ◽  
Vol 2 (23) ◽  
pp. 1249-1257 ◽  
Author(s):  
F. Michael Sawatzki ◽  
Alrun A. Hauke ◽  
Duy Hai Doan ◽  
Peter Formanek ◽  
Daniel Kasemann ◽  
...  
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors ◽  
Organic Solar Cells ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Field Effect Transistors ◽  
Electrical Power ◽  
Strong Impact ◽  
Organic Field Effect Transistor ◽  
Effect Transistor

ABSTRACTTo benefit from the many advantages of organic semiconductors like flexibility, transparency, and small thickness, electronic devices should be entirely made from organic materials. This means, additionally to organic LEDs, organic solar cells, and organic sensors, we need organic transistors to amplify, process, and control signals and electrical power. The standard lateral organic field effect transistor (OFET) does not offer the necessary performance for many of these applications. One promising candidate for solving this problem is the vertical organic field effect transistor (VOFET). In addition to the altered structure of the electrodes, the VOFET has one additional part compared to the OFET – the source-insulator. However, the influence of the used material, the size, and geometry of this insulator on the behavior of the transistor has not yet been examined. We investigate key-parameters of the VOFET with different source insulator materials and geometries. We also present transmission electron microscopy (TEM) images of the edge area. Additionally, we investigate the charge transport in such devices using drift-diffusion simulations and the concept of a vertical organic light emitting transistor (VOLET). The VOLET is a VOFET with an embedded OLED. It allows the tracking of the local current density by measuring the light intensity distribution.We show that the insulator material and thickness only have a small influence on the performance, while there is a strong impact by the insulator geometry – mainly the overlap of the insulator into the channel. By tuning this overlap, on/off-ratios of 9x105 without contact doping are possible.

Growth direction dependent separate-channel charge transport in organic weak charge-transfer co-crystal of anthracene-DTTCNQ

2022 ◽  
Author(s):  
Hui Jiang ◽  
Jun Ye ◽  
Peng Hu ◽  
Shengli Zhu ◽  
Yanqin Liang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Transport ◽  
Electronic Properties ◽  
Single Crystals ◽  
Organic Semiconductors ◽  
Crystal Engineering ◽  
Molecular Crystal ◽  
Growth Direction ◽  
Weak Charge ◽  
Separate Channel

Co-crystallization is an efficient way of molecular crystal engineering to tune the electronic properties of organic semiconductors. In this work, we synthesized anthracene-4,8-bis(dicyanomethylene)4,8-dihydrobenzo[1,2-b:4,5-b’]-dithiophene (DTTCNQ) single crystals as a template to...

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