nanoHUB-U: Organic Electronic Devices
A free self-paced course on organic electronic materials, covering molecular properties of organic semiconductors, microstructural characterization of organic semiconductors, and charge generation and transport, optoelectronic characterization, and device application of organic semiconductors.
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Organic electronic materials are defined broadly as carbon-based materials that are capable of transporting charge both in liquid-supported systems and in the solid state. While the exact molecular architectures of the materials may vary based on the desired functionality and ultimate device application, these materials due not necessarily rely on a high degree of crystallinity or band-like transport to shuttle charges in response to stimuli (e.g., an applied electric field). This is in direct contrast to many systems based on inorganic semiconductors and conductors.
Traditionally, two classes of these organic electronic materials have emerged: 1) small molecules and 2) polymers. While each class has its own set of positive aspects, drawbacks, processing conditions, and the ultimate cost-effectiveness many of the fundamental transport physics between the two classes of materials remain the same, although some distinctions do exist. In this course, we will draw on the similarity and distinctions of these two classes. Furthermore, we will evaluate how these materials can be implemented successfully in established (e.g., organic light-emitting devices (OLEDs), organic photovoltaic (OPV) devices) and emerging (e.g., thermoelectric (TE) generators, flexible memory devices) organic electronic modules. In this way, we aim to train the students of the course in the ability to tie molecular transport phenomena with macroscopic device response such that they are well-prepared to analyze, troubleshoot, and design the next generation of organic electronic materials and devices.
Who Should Take This Course
The target audience for this course is any group of persons with a direct or indirect interest in how organic electronic materials can be utilized to create the next-generation of energy conversion, energy storage, and energy reduction devices. We define next-generation devices as those that go beyond the current state-of-the-art with respect to responsiveness, form factor, flexibility, stretchability, and wearability. The materials covered in this course will allow a wide audience to apply fundamental physical phenomenon to design devices in the realms of advanced biomedical diagnostic devices to energy conversion devices that can be embedded into fabric for common clothing. Therefore, the only true limit is the imagination of the person enrolled in the course. Typically, students are at the second year or higher of their undergraduate studies. As such, a wide variety of undergraduate-level students have completed this course. Furthermore, we have had many graduate students take this course with great pleasure and success. As such, we envision that any student with a degree in science or engineering, and whether they are in academia or industry currently, would find this course to be both enjoyable and intellectually rewarding.
Course is suited for undergraduates with two semesters of general chemistry, two semesters of general physics, and one semester of organic chemistry. Familiarity with solid-state physics or elementary circuits is recommended but not required.
Unit 1 - Semiconductor Synthesis and Molecular Characterization
L1.1: An Introduction to Organic Electronic Materials
L1.2: Synthesis of Poly (3-alkylthiophenes) (P3ATs)
L1.3: Synthesis of Low Bandgap Polymers
L1.4: Molecular and Thermal Characterization
L1.5: Structural and Optical Characterization
Unit 2 - Electronic Structure
L2.1: Atomic and Molecular Orbitals
L2.2: The Schrodinger Equation
L2.3: Application of the Schrodinger Equation
L2.4: The Fermi Energy and The Density of States
L2.5: Carrier Densities in Intrinsic Semiconductors
Unit 3 - Charge Transport
L3.1: Charge Transport via a Hopping Mechanism
L3.2: Doping in Semiconducting Materials
L3.3: Multiple Trap and Release(MTR) Model
L3.4: Transport in Disordered Semiconductors
L3.5: Organic Field-Effect Transistors
Unit 4 - Field-Effect Transistors and Light Emitting Devices
L4.1: Overview of Organic Photovoltaic Devices
L4.2: Characterizing Device Parameters in OPVs
L4.3: Nanostructural Impacts in OPV Devices
L4.4: Interfacial Modifying Layers in OPV Devices
L4.5: Emerging Trends in OPV Devices
Unit 5 - Photovoltaic and Emerging Devices
L5.1: Introduction to Organic Light-emitting Devices
L5.2: Design Considerations for OLEDs
L5.3: Introduction to Polymer Thermoelectric Devices
L5.4: State-of-the-Art in Polymer Thermoelectrics
L5.5: Course Review and Summary
Applications of Concepts
This course gives an introduction to the optical properties, transport physics, and device operation of organic electronics. This course will review how the molecular architecture of small molecule and polymer semiconductors can be tuned to alter the optoelectronic properties of the materials in solution and in the solid state. A number of relevant materials interactions will be covered, including: photoexcitation and recombination, intermolecular charge transport mechanisms, and energy transfer processes. Furthermore, the mechanism of transport in organic electronic materials, which generally are highly-disordered relative to traditional inorganic semiconductors, will be covered in great detail. Additionally, we will elucidate how these processes are relevant to applications such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), organic photovoltaic (OPV) devices (i.e., flexible solar cells), organic memory elements, and organic thermoelectric (TE) generators. Importantly, all of these devices are compatible with low-cost, high-throughput fabrication techniques, flexible substrates, and lightweight devices. The application of the fundamental physics to these applied devices will allow the students to evaluate the current state-of-the-art in organic electronic devices and also to begin to realize the ultimate performance limit of these materials and devices.
As the completion of this course, the students should be able to perform the following learning objectives, as classified by one of the three major sections.
- Molecular Properties of Organic Semiconductors. Interpret spectroscopic, chromatographic, and molecular characterization data in order to predict the structure of the organic semiconductor; and explain how the molecular structure of an organic semiconductor will affect its thermal, structural, and optoelectronic properties.
- Microstructural Characterization of Organic Semiconductors. Explain how x-ray and neutron scattering can be utilized to determine the Angstrom and nanometer length scale structural features of the organic semiconductors; apply principles of electron microscopy to comprehend how to image soft materials; and utilize the nanostructure of the material to predict how the organic semiconductor will perform when incorporated into organic electronic devices.
- Charge Generation and Transport, Optoelectronic Characterization, and Device Application of Organic Semiconductors. Explain how molecular orbital levels are related to the optoelectronic properties of organic semiconductors; distinguish between different models for charge transport in organic semiconductors; describe clearly the difference between charge generation and transport in organic and inorganic semiconductors; explain how organic electronic devices operate and how apply known equations to evaluate device performance; critique the potential for organic electronic materials to supplement or replace inorganic semiconducting devices.
- A free nanoHUB.org account is required to access some course components.
- Homework exercises will be given with solutions and tutorials.
- Online quizzes to quickly assess understanding of material after most video lectures.
- Practice exams for each module.
Organic Electronic Devices first published on edX, February 2015 and nanoHUB-U, May 2015.
This self-paced course is available at no cost.
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