Michael Lawrence Chabinyc - US grants

ARRA STATEMENT:

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

TECHNICAL SUMMARY:

This collaborative project aims to study the detailed interfacial structure of semiconducting and dielectric polymers. The influence of interfacial interactions on the molecular ordering and the electrical properties of rigid-rod semiconducting polymers is poorly understood. The proposed experiments will attempt to disaggregate, for the first time, the impact of molecular organization, dipolar interactions, and roughness on charge transport at interfaces of semiconducting polymers. The tasks to achieve this goal include: (1) controlled fabrication of interfaces of semiconducting and dielectric polymers, (2) characterization of the microstructure at their interface, and (3) electrical characterization to determine the electronic structure at the interface. Advanced synchrotron x-ray scattering methods, such as soft x-ray scattering, will be used to interrogate the structure at polymer-polymer interfaces. Detailed temperature dependent electrical measurements on thin film transistors will be used to examine the electronic density of states in the semiconducting polymer. The successful outcome of this effort will be an understanding of how molecular interactions at interfaces affect the transport of carriers in semiconducting polymers.


NON-TECHNICAL SUMMARY:

Semiconducting polymers are important materials for low-cost flexible electronics such as displays, distributed sensors, and solar cells. The detailed understanding of these materials gained through this research will be important for their future commercialization. The proposed collaborative research is highly multidisciplinary and will train students in a combination of materials science, chemistry, and electronics. Graduate students and the principal investigators will mentor summer high school and undergraduate students from underrepresented minorities allowing them to gain exposure to advanced research at large-scale synchrotron research facilities. The potential of organic electronics technology for society will be disseminated through demonstrations at local science night programs. This project will also aid in the development of a new integrated lecture course sequence on organic electronic materials at UCSB. International collaboration will be fostered through collaboration with researchers in the U.K.

This award continues the funding for the International Materials Institute at the University of California at Santa Barbara, called the International Center for Materials Research (ICMR), which was founded in 2004. During the next five years, ICMR will continue to promote international research collaborations and education in materials science and engineering with the goals to (1) enable ground-breaking discoveries by facilitating multidisciplinary, international collaborations, (2) provide opportunities for junior researchers to develop the skill needed to excel in a global research environment and (3) integrate materials research experiences with an awareness of environmental and developing world issues into undergraduate curricula. The IMI covers thematic research programs in a broad range of experimental and theoretical materials science topics, such as, multifunctional materials and complex oxides, strongly correlated materials, materials theory for experimental problems, multiscale modeling of electrochemical systems for energy applications. Each research program begins with an international workshop to define pressing issues in the field, followed by a school to train graduate students and junior researchers, and extended international exchange visits by students and faculty. Finally a wrap-up conference on each research program allows progress to be summarized, future directions to be defined, and facilitates initial evaluation of program effectiveness. This IMI serves as an umbrella for existing and new world-wide networks of collaborations at the individual researcher and institutional levels. International research collaborations encompass many countries in Asia, Europe, and Latin America while workshops and schools include participants from across the globe. Furthermore, the IMI offers international research fellowships, travel grants to pursue research in foreign laboratories, undergraduate exchange program, student-led engineering design projects and travel fellowships focused on materials research related issues in emerging regions of the world, as well as student science reporter apprentice opportunities. The IMI management team consists of UCSB faculty members, administrative coordinators, and a local steering committee. A U.S.-wide advisory board helps solicit and select ideas for new programs and an international advisory board provides general guidance for IMI activities.

In this International Collaboration in Chemistry between US Investigators and their Counterparts Abroad (ICC) project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division and the Office of International Science and Engineering, Michael Chabynic and Craig Hawker of the University of California at Santa Barbara will synthesize hole and electron transporting polymers that can be utilized in nanoimprint lithography to form layers for organic photovoltaic devices. The approach is to synthesize poly(alkyl selenophene)s and copolymers of poly(cyclopenta-dithiophene) with poly(benzothiadiazole) containing thermal and photo-crosslinkable side groups, and these donor polymers will be examined for use in nanoimprint lithography. Next, novel poly(benzotrithiophene) donor polymers and fused thiazole and selenazole acceptor polymers will be prepared and studied. Conformal parylene C coatings will be stacked onto the nanoimprinted donor polymer layer before the double imprint of the acceptor polymer is deposited. Additionally, non-crystalline dyes will be added to the donor layer that should migrate to the surface upon annealing of the donor layer in the imprinting process. These interfacial layers should help to reduce the kinetics of back electron transfer during the charge separation step. This work includes an international collaboration with Prof. Martin Heeney and Prof. Iain McCulloch of the Imperial College London, U.K. Profs. Heeney's and McCulloch's work will be funded by the Engineering and Physical Sciences Research Council (EPSRC). The broader impacts involve training graduate students and enhancing infrastructure for research and education through establishment of an international collaboration between universities in the U.S. and the U.K. The collaborators will endeavor to develop course materials on organic electronics that can be used in the curricula at both universities.

Organic polymer-based solar cells show great technological promise but have significant drawbacks in terms of low efficiencies and significant processing problems. This research will enhance our fundamental understanding about how organic polymers can be used to form solar cells and capture light and turn it into electrical energy. By exploring new types of polymers, this research could lead to easier to process and less expensive solar cell technologies.

In this collaborative project, four scientists at the University of California - Santa Barbara will investigate the design, synthesis and incorporation of new "electroactive polymer surfactant" (EPS) molecules in all-organic polymer photovoltaic materials. The aim of this research is to overcome some of the key stumbling blocks that have plagued other researchers investigating polymer photovoltaic materials, based upon bulk heterojunction systems. The work will be organized around the following three goals: (1) the development of physics-based models and efficient numerical methods for the prediction of phase separation in blends of rod-like polymers with multifunctional copolymer surfactants; (2) the synthesis of new homopolymers and functional block copolymers/oligomers comprising p-type and n-type backbones with a central electronically active moiety, using the design characteristics from (1); and (3) the characterization of the morphology of the blends as a function of composition and process conditions. The Principal Investigators will simultaneously develop a multifaceted educational program in solar energy research, including programs for high-school teachers, workshops for young scientists, and international collaborative experiences for graduate students.

Efficient conversion of solar to electrical energy is likely to be one of the most important means of powering the planet in a sustainable way. Current materials for the conversion of sunlight to electricity are hampered by low efficiency and high cost. Work like that proposed in the present proposal seeks to find new alternatives that circumvent these problems. In particular, organic polymer (plastic) photovoltaic materials show promise as inexpensive alternatives to conventional semiconductor photovoltaic materials. Besides producing new kinds of materials for solar energy conversion, the Principal Investigators of this proposal hope to produce new kinds of scientists with the interdisciplinary expertise needed to make significant contributions to challenging scientific as well as societal problems.

TECHNICAL SUMMARY

The connection between charge transport and molecular order on intermediate length scales in films of semiconducting polymers will be examined. In most electrical devices, semiconducting polymer chains do not span the distance between the electrodes and the resulting electrical properties are the result of charge transport both along the chains and from chain-to-chain. Through a collaborative effort between scientists at UCSB and NCSU the charge transport pathways in semiconducting polymers will be studied by: 1) measuring the in-plane bulk and interface correlation length of the backbone of semiconducting polymers using a combination of physical and electrical characterization methods and 2) investigating transport in model block co-polymer systems with varying energetic structure to uncover how both positive and negative carriers are transported in complex systems. This work will use a novel polarized soft X-ray scattering method to probe the backbone correlation length that will enable a greater understanding of the connection between morphology and electrical transport. The scattering techniques developed in this work will have impact on characterization of both semiconducting and conventional polymers.


NON-TECHNICAL SUMMARY

Conjugated polymers have tremendous potential for use in cheap, flexible, light-weight devices as transistors in simple circuits, light emitting diodes, and solar cells. Improvement of our control of the properties of electrically conducting polymers will enable new types of electronic devices for use in energy conversion and biomedical diagnostics. This work will focus on the determination of the pathways of charge transport in conjugated polymers. Research in polymer electronics is highly multidisciplinary and will provide training for graduate students in materials science, chemistry, and microelectronics. The PIs and graduate students will also provide lab space and training for promising undergraduate students from underrepresented groups to advance their future careers in science and engineering. Outreach to children to promote science education in the local school districts will be done through demonstrations of flexible electronics devices by graduate student researchers at local science nights.

NON-TECHNICAL SUMMARY
This project is funded by the Division of Materials Research and the Division of Chemistry through the Designing Materials to Revolutionize and Engineer our Future (DMREF) program. Organic polymers are pervasive in modern everyday life, and they have enabled advances in areas ranging from health care to computer technology. The great promise of polymers is their versatility. For example, recent systems have been designed to conduct electricity. Conducting polymers are potential game-changers because they can be dissolved in solvents and printed like inks on flexible substrates for low-cost electronics and sensors. Fabrication of electronic devices using conducting polymers requires the ability to predict how the printing process affects their performance. The PIs and students on this project will develop new materials using an approach in which computational methods guide the design and accelerate the discovery of high performance conducting polymers. The project will have significant impact on the future scientific and engineering workforce with graduate student researchers gaining critical new skills in combining computer simulations and physical experiments. The research team will also perform outreach to the public through educational activities in local K-12 schools.

TECHNICAL SUMMARY
Charge transport in semiconducting polymers is typically described as two-dimensional due to the molecular packing structure in many ordered materials. Recent observations suggest that hierarchical nanostructures form in semiconducting polymers and suggest the possibility of multi-dimensional transport pathways. This project aims to accelerate discovery of materials through feedback between computational and experimental results. The research team will develop highly efficient computational methodologies to predict processing methods and materials that lead to hierarchical 3D-transport pathways. A goal of the research is to develop new computational methodologies for massively parallel computations to take advantage of advances in computational hardware. New conjugated polymers will be designed with guidance from theory, and physical measurements will be made to benchmark the computational framework, in order to understand the evolution of structure during solution casting. Scalable models to understand the role of domain boundaries in charge transport in semiconducting polymers will be developed using structural maps from electron microscopy. Open source codes and large datasets for benchmarking computational studies of charge transport in semiconducting polymers are a focus of the research.

Non-Technical Abstract

Organic semiconductors are carbon-based materials, similar to dyes, that conduct electricity. They can be dissolved in solvents and printed using inkjet-printing on flexible substrates for use in low-cost electronics such as displays and sensors. Light emitting diodes based on organic semiconductors are already commercially available in mobile phones. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research, this research project expands their use through the study of their fundamental physical properties such as their electrical conductivity, and explores possibilities for converting excess thermal energy to electrical power. The project has significant impact on the future scientific workforce because graduate student researchers carrying out the research gain significant training in multidisciplinary materials science and engineering. The research team also performs outreach to the public through educational activities in local K-12 schools.


Technical Abstract

A key challenge in molecular organic electronic materials is the control of their electronic properties through solid state ordering. Electrical doping of organic semiconductors is important for electrode layers in organic light emitting diodes and solar cells and in emerging thermoelectric applications. The research in this project examines how the crystalline order in solution processed organic semiconductors, both in neat films and in blends with acceptors, affects their electrical conductivity and electronic structure. The intrinsic properties of electrical conduction are compared in samples doped by molecular acceptors in model bilayer structures and in the bulk. Thermopower measurements and advanced x-ray structural characterization are carried out to determine how the microstructure and electronic structure of organic molecular solids evolve upon electrical doping. Gated thermopower measurements are used to determine the electronic structure of undoped materials to gain insight into their electronic structure. This research provides insight into new means to control the electrical conductivity of organic semiconductors in order to determine the limits of the electrical properties of these important materials systems.

Non-technical description: This project will develop and maintain a public website for the National Science Foundation's (NSFs) Designing Materials to Revolutionize and Engineer our Future (DMREF) program. The DMREF program has built a solid base of materials research that has been accelerated through the use of the computationally-led and data-driven principles promoted by the Materials Genome Initiative (MGI). One of the goals of MGI is to render the digital outputs of DMREF funded projects available and useful to the community. In order to increase the impact of DMREF research, it is critical to increase its visibility through a public website. This website will disseminate the research of the program to the scientific community and the general public. The website will contain a database of DMREF teams and their research topics. Highlights from each of these teams will also be made available through the website. Activities and conferences related to the DMREF program will be posted to the site and archived. Training materials will be made available to facilitate the interdisciplinary training of students and thus contribute to the development of a modern workforce.

Technical description: The goals of the Designing Materials to Revolutionize and Engineer our Future (DMREF) program at the National Science Foundation (NSF) are consistent with the Materials Genome Initiative (MGI) which accelerates the pace of materials research through computationally led and data driven methods. This highly interdisciplinary program coordinates activities with MGI-related efforts funded by other federal agencies. As such, there is a need to connect PIs and their research in real-time. Webpages have become a common tool for conveying information in the modern era. This project will develop and maintain a website for the DMREF program that will contain information about the DMREF teams and their research. In order to increase the impact of future DMREF research, it is critical to increase its visibility through a public website. This website will enable connection between PIs that will lead to the formation of new teams to address contemporary materials research problems. A goal of the MGI and DMREF is to accelerate the transition of materials through the materials development continuum from discovery to deployment. This website will facilitate this process by rendering DMREF research visible to potential industrial partners. The website will also enable students from all levels of education to learn about the DMREF program and provide resources to enable them to prepare for future careers in academia or industry.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Electron back-scattered diffraction (EBSD) has evolved into a widespread and powerful characterization technique for the mapping and analysis of phases in materials, providing key information about crystal orientation, morphologies, lattice strain, topology, and crystallographic texture. The advent of direct electron detection that circumvents inefficient conversion between electrons and photons has revolutionized the field of transmission electron microscopy owing to single-electron sensitivity for low-dose imaging and ultrafast detection for time-resolved studies, but its use in scanning electron microscopes (SEMs) is in its infancy. An award is made to the University of California Santa Barbara to develop an ultrafast and ultrasensitive direct electron EBSD instrument for the widely accessible SEM platform, providing a rich opportunity for materials research that are hindered by electron beam damage and temporal limitations of detectors. The development project improves on the state-of-the-art EBSD acquisition speed and enhances the sensitivity through a new sensor design, unlocking the most vexing challenges in the rapid 3D characterization of additively manufactured materials and emerging dose-sensitive energy storage and conversion materials plagued by beam damage. The award will ensure engagement with the community and early-career researchers via a yearly open house hosted by the shared user facility, as well as with REU and RET projects through partnerships with the Materials Research Laboratory and the Quantum Foundry at UC Santa Barbara. The developed instrumentation and simulation tools will also be integrated with the Center for Scientific Computing, which promotes the effective use of High Performance Computing in the research and teaching environment.

The next-generation direct-detection EBSD instrument will be optimized for electron beam energies of 3kV to 30kV with single-electron sensitivity, and a small sensor form factor permitting flexible location within the microscope chamber. For materials that are damage-prone, such as organic crystalline materials, limiting the electron dose is critical and detection yield becomes paramount, especially at low energies. The developed instrument will enable the detection of rich material information encoded in electron diffraction, circumventing longstanding issues of low-damage threshold and weak scattering signals. Metallic alloys and battery materials also benefit from high detection sensitivity and low-kV operation, revealing structural features such as dislocation cells in additively manufactured materials and enabling the evolution of microstructure at rates that can keep up with in operando device observations.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.