Download Free Monte Carlo Simulations Of Charge Transport In Organic Semiconductors Book in PDF and EPUB Free Download. You can read online Monte Carlo Simulations Of Charge Transport In Organic Semiconductors and write the review.

Thin film organic semiconductors have applications in electronic devices such as transistors, light emitting diodes, and organic solar cells. The performance of such devices depends on the mobility of the charge carriers which is strongly affected by the morphology of the material. In this work, we perform Monte Carlo simulations to study charge transport in lattice models of homogeneous and heterogeneous materials. The model device consists of a layer of the material between two electrodes at different potentials. Charge carriers are injected from the electrodes and move by hopping under the influence of the electric field and Coulomb interactions. To model the effect of polymer chain connectivity on charge transport we include an energetic barrier to hopping between sites on different chains. We measure current-voltage (I-V) characteristics of model devices and determine the mobility of the charge carriers from the slope of the I-V curves in the ohmic regime. We validate our algorithms with simulations of simple devices consisting of two parallel layers of donor and acceptor materials between the electrodes. To study the effect of ordered domains in polymeric semiconductors we simulate charge transport in a recently developed lattice model for polymers that undergo an order-disorder transition. We find that ordering in the material leads to strong anisotropies with increased mobility for transport parallel to the ordered domains and reduced mobility for perpendicular transport.
A new multiscale method is presented for modeling charge transport across a semi-conductor heterointerface. It has the advantage of increase predictive power due to its treatment of the detailed mixing between Bloch and Tamm electronic states in the interface region; this is of critical importance when a transmission or reflection is accompanied by large changes in perpendicular wavevector, and in the presence of multiple transmission and reflection channels. The electron-phonon interaction is then examined in bulk silicon within the local density functional formalism. Intravalley and intervalley deformation potentials are calculated for a variety of transitions, and the model is compared with available data from both experimental and alternative calculation methods. The formalism developed in this thesis for the calculation of electron-phonon interaction strength is then applied to the calculation of matrix elements for an exhaustive set of transitions throughout the entire Brillouin zone and over a wide range of energies, taking into account the details of each phonon mode. These matrix elements are then incorporated into a unique Monte Carlo charge transport simulator with which transport statistics are calculated. Finally, a new method is presented for the calculation of spectral functions in crystalline solids.
In the field of organic semiconductors researchers and manufacturers are faced with a wide range of potential molecules. This work presents concepts for simulation-based predictions of material characteristics starting from chemical stuctures. The focus lies on charge transport – be it in microscopic models of amorphous morphologies, lattice models or large-scale device models. An extensive introductory review, which also includes experimental techniques, makes this work interesting for a broad readership. Contents: Organic Semiconductor Devices Experimental Techniques Charge Dynamics at Dierent Scales Computational Methods Energetics and Dispersive Transport Correlated Energetic Landscapes Microscopic, Stochastic and Device Simulations Parametrization of Lattice Models Drift–Diusion with Microscopic Link
To aid the design of organic semiconductors, we study the charge transport properties of organic liquid crystals and single crystals. The aim is to find structure-property relationships linking the chemical structure as well as the morphology with the bulk charge carrier mobility of the compounds. To this end, molecular dynamics (MD) simulations are performed yielding realistic equilibrated morphologies. Partial charges and molecular orbitals are calculated using quantum chemical methods. The molecular orbitals are then mapped onto the molecular positions and orientations, which allows calculation of the transfer integrals between nearest neighbors using the molecular orbital overlap method. Thus realistic transfer integral distributions and their autocorrelations are obtained. In case of organic crystals two descriptions of charge transport, namely semi-classical dynamics (SCD) and kinetic Monte Carlo (KMC) based on Marcus rates, are studied. In KMC one assumes that the wave function is localized on one molecule, while in SCD it is spread over a limited number of neighboring molecules. The results are compared amongst each other and, where available, with experimental data.
This volume presents the application of the Monte Carlo method to the simulation of semiconductor devices, reviewing the physics of transport in semiconductors, followed by an introduction to the physics of semiconductor devices.
This volume presents the application of the Monte Carlo method to the simulation of semiconductor devices, reviewing the physics of transport in semiconductors, followed by an introduction to the physics of semiconductor devices.
To aid the design of organic semiconductors, we study the charge transport properties of organic liquid crystals, i.e. hexabenzocoronene and carbazole macrocycle, and single crystals, i.e. rubrene, indolocarbazole and benzothiophene derivatives (BTBT, BBBT). The aim is to find structure-property relationships linking the chemical structure as well as the morphology with the bulk charge carrier mobility of the compounds. To this end, molecular dynamics (MD) simulations are performed yielding realistic equilibrated morphologies. Partial charges and molecular orbitals are calculated based on single molecules in vacuum using quantum chemical methods. The molecular orbitals are then mapped onto the molecular positions and orientations, which allows calculation of the transfer integrals between nearest neighbors using the molecular orbital overlap method. Thus we obtain realistic transfer integral distributions and their autocorrelations. In case of organic crystals the differences between two descriptions of charge transport, namely semi-classical dynamics (SCD) in the small polaron limit and kinetic Monte Carlo (KMC) based on Marcus rates, are studied. The liquid crystals are investigated solely in the hopping limit. To simulate the charge dynamics using KMC, the centers of mass of the molecules are mapped onto lattice sites and the transfer integrals are used to compute the hopping rates. In the small polaron limit, where the electronic wave function is spread over a limited number of neighboring molecules, the Schroedinger equation is solved numerically using a semi-classical approach. The results are compared for the different compounds and methods and, where available, with experimental data. The carbazole macrocycles form columnar structures arranged on a hexagonal lattice with side chains facing inwards, so columns can closely approach each other allowing inter-columnar and thus three-dimensional transport. When taking only intra-columnar transport into account, t.
Monte Carlo simulation is now a well established method for studying semiconductor devices and is particularly well suited to highlighting physical mechanisms and exploring material properties. Not surprisingly, the more completely the material properties are built into the simulation, up to and including the use of a full band structure, the more powerful is the method. Indeed, it is now becoming increasingly clear that phenomena such as reliabil ity related hot-electron effects in MOSFETs cannot be understood satisfac torily without using full band Monte Carlo. The IBM simulator DAMOCLES, therefore, represents a landmark of great significance. DAMOCLES sums up the total of Monte Carlo device modeling experience of the past, and reaches with its capabilities and opportunities into the distant future. This book, therefore, begins with a description of the IBM simulator. The second chapter gives an advanced introduction to the physical basis for Monte Carlo simulations and an outlook on why complex effects such as collisional broadening and intracollisional field effects can be important and how they can be included in the simulations. References to more basic intro the book. The third chapter ductory material can be found throughout describes a typical relationship of Monte Carlo simulations to experimental data and indicates a major difficulty, the vast number of deformation poten tials required to simulate transport throughout the entire Brillouin zone. The fourth chapter addresses possible further extensions of the Monte Carlo approach and subtleties of the electron-electron interaction.
Particle simulation of semiconductor devices is a rather new field which has started to catch the interest of the world's scientific community. It represents a time-continuous solution of Boltzmann's transport equation, or its quantum mechanical equivalent, and the field equation, without encountering the usual numerical problems associated with the direct solution. The technique is based on first physical principles by following in detail the transport histories of indi vidual particles and gives a profound insight into the physics of semiconductor devices. The method can be applied to devices of any geometrical complexity and material composition. It yields an accurate description of the device, which is not limited by the assumptions made behind the alternative drift diffusion and hydrodynamic models, which represent approximate solutions to the transport equation. While the development of the particle modelling technique has been hampered in the past by the cost of computer time, today this should not be held against using a method which gives a profound physical insight into individual devices and can be used to predict the properties of devices not yet manufactured. Employed in this way it can save the developer much time and large sums of money, both important considerations for the laboratory which wants to keep abreast of the field of device research. Applying it to al ready existing electronic components may lead to novel ideas for their improvement. The Monte Carlo particle simulation technique is applicable to microelectronic components of any arbitrary shape and complexity.