Organic semiconductor

About: Organic semiconductor is a research topic. Over the lifetime, 15905 publications have been published within this topic receiving 533881 citations.

Tuning magnetoresistance between positive and negative values in organic semiconductors.

Abstract: Magnetic-field-dependent injection current, namely magnetoresistance, is readily observable in organic semiconductor devices. This provides a non-contact approach to tune organic optoelectronic properties by using a magnetic field. Here, we demonstrate that this magnetoresistance can be changed between positive and negative values by adjusting the dissociation and charge reaction in excited states through changing the bipolar charge injection in organic light-emitting diodes. This finding reveals that the magnetic-field-dependent generation of secondary charge carriers from the dissociation and charge reaction affects the injection current by forming further space charges at the organic–electrode interfaces and therefore accounts for the tunable magnetoresistance. Furthermore, the dissociation and charge reaction have opposite dependences on magnetic field in the generation of secondary charge carriers, consequently leading to negative and positive magnetoresistance, respectively. As a result, adjusting the dissociation and charge reaction in excited states provides a convenient pathway to tune the magnetoresistance in organic semiconductors.

Dynamics of the intermolecular transfer integral in crystalline organic semiconductors

Abstract: In organic crystalline semiconductor molecular components are held together by very weak interactions and the transfer integrals between neighboring molecular orbitals are extremely sensitive to small nuclear displacements. We used a mixed quantum chemical and molecular dynamic methodology to assess the effect of nuclear dynamics on the modulation of the transfer integrals between close molecules. We have found that the fluctuations of the transfer integrals are of the same order of magnitude of their average value for pentacene and anthracene. Under these conditions the usual perturbative treatment of the electron-phonon coupling is invalid, the band description of the crystal breaks down and the charge carriers become localized. Organic crystals of pentacene and anthracene, even in the absence of defects, can be regarded as disordered media with respect to their charge transport properties. These results suggest that the dynamic electronic disorder can be the factor limiting the charge mobility in crystalline organic semiconductors.

Interface‐Controlled, High‐Mobility Organic Transistors

Abstract: The achievement of high mobilities in field-effect transistors (FETs) is one of the main challenges for the widespread application of organic conductors in devices. Good device performance of a single-crystal pentacene FET requires both removal of impurity molecules from the bulk and the manipulation of interface states. A reliable method for fabricating FETs, which involves careful control of the semiconductor/gate interface (see figure), is presented.

Synthesis and device characterisation of side-chain polymer electron transport materials for organic semiconductor applications

Abstract: Improved syntheses and polymerisations are reported of monomers bearing electron transporting substituents based on 2,5-diphenyloxadiazole and 2,3-diphenylquinoxaline attached directly to a vinyl group. By copolymerisation and by use of mixtures of homopolymers, these materials have been incorporated into light emitting polymer devices in which hole conduction properties are provided by 4-vinyltriphenylamine groups. High luminescence efficiency is achieved by use of a fluorescent additive. The resulting devices show narrow emission bands and high brightnesses, except in the case of those based on a diphenyloxadiazole–triphenylamine polymer blend. Thermal analysis data are equivocal but we present evidence that in this system, but not the quinoxaline blend, phase separation occurs. The minority charge carrying capacity of the homopolymers is probed: it is shown that the quinoxaline derivative has hole blocking properties superior to those of the oxadiazole polymer and is a good candidate for use in optimised devices.

The role of chemical design in the performance of organic semiconductors

Abstract: Organic semiconductors are solution-processable, lightweight and flexible and are increasingly being used as the active layer in a wide range of new technologies. The versatility of synthetic organic chemistry enables the materials to be tuned such that they can be incorporated into biological sensors, wearable electronics, photovoltaics and flexible displays. These devices can be improved by improving their material components, not only by developing the synthetic chemistry but also by improving the analytical and computational techniques that enable us to understand the factors that govern material properties. Judicious molecular design provides control of the semiconductor frontier molecular orbital energy distribution and guides the hierarchical assembly of organic semiconductors into functional films where we can manipulate the properties and motion of charges and excited states. This Review describes how molecular design plays an integral role in developing organic semiconductors for electronic devices in present and emerging technologies. Many present and emerging electronic devices make use of organic semiconductors in view of their readily tuneable molecular and electronic structures. This Review describes the importance of analytical and computational tools in studying the molecules as well as their hierarchical self-assemblies, in which the motion of charges and excited states govern device properties.