Sean E. Shaheen - US grants

Technical: This project aims for greater fundamental understanding of the nature of electronic and structural defects in organic photovoltaic (OPV) devices. At present, the origin and nature of such defects are poorly understood, as is their impact on device performance. This project will analyze defects in existing and new materials for OPV devices through a variety of experimental techniques, including impedance spectroscopy, carrier transport measurements, and OPV device fabrication and testing. The experimental results will be closely coupled with Monte Carlo computational simulations of charge transport and recombination processes and finite element calculations of OPV device performance. Attempts at mitigating or removing defects from the devices will be carried out through techniques such as pulsed electrical biasing to induce either subtle changes in the local-scale morphology or removal of macroscopic short-circuit defects.

Non-technical: The project addresses basic research issues in a topical area of materials science with technological relevance in electronics and photonics. Successful outcome of the project will result in more efficient and robust organic photovoltaic devices that provide an avenue to low cost solar energy utilizing a technology that is easily scaled to large area and high throughput manufacturing. Fundamental progress in the science and engineering of organic photovoltaics can be readily transitioned to application via existing start-up OPV companies that are striving to bring the technology to the point of cost-efficient, large area solar power conversion. Integration of research and education will be emphasized providing students with opportunities and challenges across the fields of physics, chemistry, and engineering, and through the collaborative nature of the project. A female undergraduate student will be working on the project, and it is expected that this experience will accelerate her learning process and help launch her graduate career in applied physics or engineering. Outside the University, the project will reach out to the local Denver community via interaction with the Wings over the Rockies Air & Space Museum. Through an existing close relationship with the museum, the PI and students will build new exhibits at the museum that expose the general population to the science and engineering of solar energy and organic and other photovoltaic technologies. He will also provide curriculum for summer camps and programs at the museum that reach out to Boy and Girl Scout troops, minorities, and children in at-risk populations.

This collaborative project brings together faculty and scientists at the University of Denver and the University of Colorado at Boulder to study new materials and concepts in organic photovoltaics (OPV). It combines new mathematical methods to describe photonic processes with novel plasmonic nanostructures for enhancing optical absorption and new organic semiconductors for control of exciton flow and charge carrier dynamics. The theoretical foundations of linear and nonlinear processes in surface plasmons and their interactions with organic chromophores are explored, and the interplay between surface plasmons and Förster Resonant Energy Transfer (FRET) is investigated. New organic molecules are synthesized that incorporate graphenic and other moieties with exceptional charge transport and excited-state properties along with liquid-crystalline functionality for improved molecular ordering. The overall goal is to enhance the density of excitons created in OPV devices to enable higher efficiencies as well as coherent control of excited state dynamics and multiexciton phenomena. The work entails significant collaborations with the National Renewable Energy Laboratory and the University of Toronto.

This project aims to advance the fundamental knowledge of OPV materials and mechanisms and to provide impetus for moving OPV to the broader market as a low-cost solar energy technology that can be produced on a truly large scale. The interdisciplinary nature of the project gives graduate students and postdoctoral trainees exposure to a variety of research settings and fosters their learning and career growth. The project generates educational materials that are broadly disseminated through websites and through the National Science, Technology, Engineering, and Mathematics Education Digital Library (NSDL). Outreach activities for local high school science teachers in the Denver and Boulder areas enable hands-on experience with intensive workshops on solar energy and nanotechnology. Demonstrations, exhibits, and instructional materials are provided to Colorado institutions such as the Wings Over the Rockies Air & Space Museum and the Mamie Dowd Eisenhower Library.

With this award from the Major Research Instrumentation Program (MRI) and support from the Chemistry Research Instrumentation Program (CRIF) as well as the MPS Office of Multidisciplinary Activities (OMA), Professor Markus Raschke from the University of Colorado Boulder and colleagues Steven Cundiff, Prashant Nagpal, Thomas Perkins, and Sean Shaheen are developing an infrared scanning near-field optical microscope (IR s-SNOM) for broadband nano-imaging and spectroscopy. The instrument provides vibrational and chemical infrared imaging data with nanometer spatial resolution, high spectral resolution and single molecule sensitivity. This instrument is to enable the study of molecular self-organization and nanoscale phase separation in polymer blends, block-copolymers, liquid crystals, and biomembranes; energy and charge transfer in photosynthesis; and organic and inorganic photovoltaics. The award not only allows for the development of a new instrument but also provides training to early career scientists in instrumentation development.

The instrument development effort is being applied to projects such as: (a) studying coupling and transport in organic photovoltaics and electrochemical transistors, (b) achieving label-free access of structure and function of membrane proteins, (c) investigating inter-sub-band transitions in nano-bio-hybrid materials for solar fuel generation, and (d) probing intermolecular coupling and dynamics through local probe vibrational solvatochromism. The technical innovation in IR s-SNOM may lead to new discoveries in soft-matter and quantum materials of utility to imaging technologies.

Time-resolved in-situ metrology of organic electrochemical transistors to support the development of a dynamic device model

Abstract
Nontechnical: Organic electrochemical transistors (OECTs) are an emerging class of biocompatible organic semiconductor device that operate at very low voltages and with very high amplification. This combination of properties makes them attractive for external and implanted bioelectronics such as measuring electrical activity of muscles or neurons. However, progress is currently limited by incomplete understanding of the internal functioning of the transistors and also rudimentary fabrication methods that restrict integration and repeatability. The internal dynamics of the transistors will be studied with a number of microscopy techniques applied to operating transistors to inform the assembly of a theoretical device model. This model will guide the creation of new biomedical devices based on these transistors including the measurement of cellular action potentials.

Technical: OECTs modulate the conductivity of a polymer semiconductor by injecting ions that replace dopant polyions, reversibly transforming the polymer channel into an insulator. This study will elucidate the spatio-temporal dynamics of lithographically-fabricated OECTs, based on the conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). The proposed techniques include real-time, electrochromic microscopy to elucidate the in situ doping dynamics during switching, scanning Kelvin probe microscopy to measure the spatial distribution of polymer doping on even finer scales, and AFM to reveal polymer morphology and swelling that are critical to understanding the physiological interface. These studies will elucidate the interplay of ion transport and doping, current flow, and mechanical properties in the active channel of working devices, leading to a better understanding of the structure-function relationship and validation of the first complete transient model of OECT function. This understanding will guide the study of improved fabrication methods including UV photolithography and surfactants that have been shown to improve performance and repeatability of other organic electronic devices. Repeatable photolithographic fabrication will enable device integration and precision measurements beyond current capability. Performance of these optimized sensors will be demonstrated by integration with nerve-like and skeletal myocyte cells, which will be bio-printed onto the gates of OECT arrays and a multi-electrode array for comparison. This will be performed with the assistance of a local bio-tech firm and two CU cell biology collaborators. A low-noise, multiplexed electrical interface to the OECT array will be designed and built as part of the undergraduate and outreach program.

Lead Proposal ID: HRD 16-1649201
Principal Investigator: Sarah M Miller
Institution: University of Colorado Boulder
Proposal Title: Creating Academic Pathways in STEM (CAPS): A Model Ecosystem for Supporting Two-Year Transfer

Collaborated Proposal ID: HRD 16-1648697
Principal Investigator: Heidi Loshbaugh
Institution: Community College of Denver

Education pathways have grown increasingly complex in recent decades and today are characterized by a multitude of entry points, stops and starts, longer times to degrees, and changing career directions. As a result, the STEM "pipeline" metaphor has become outdated, and the current institutional structures are not well suited to meeting the educational needs of today's students. This project will create coordinated strategic pathways between 2-year colleges, national laboratories, industry, and the University of Colorado Boulder aimed at changing the educational landscape and facilitating opportunities for students who begin their higher education path at 2-year colleges. In doing so, these efforts will broaden participation among those matriculating in STEM majors who are ready to engage and contribute to a knowledgeable and skilled STEM workforce. This initiative will create links and strengthen pathways to establish a systematic, holistic and sustainable transfer ecosystem that will dramatically increase the number of Colorado 2-year college students that go on to pursue 4-year STEM degrees.

This project will establish a network (hub and spoke system) in STEM education that will serve as a model for regional STEM education collaboration. These efforts will create a cooperative and transformational infrastructure that streamlines STEM pathways for diverse students from 2- to 4- year colleges. By developing a student-centered infrastructure focused on lowering and eliminating barriers that inhibit 2-year college student transfer to 4-year colleges, this initiative will encourage talented 2-year college students interested in pursuing a STEM baccalaureate to successfully transfer, ultimately advancing the technical capacity of Colorado and beyond.

This RET Site: Authentic Research Experiences for Teachers (ARETe): Connecting Community College Faculty and Students to University Engineering and Computer Science Labs enhances coordination between the University of Colorado Boulder (CU) and five, 2-year degree granting community colleges (2YCs) in the Denver-Boulder metropolitan area: Arapahoe Community College, Community College of Aurora, Community College of Denver, Front Range Community College, and Red Rocks Community College. The project creates and cultivates a network of science, technology, engineering, and mathematics (STEM) 2YC faculty with specific expertise on cutting edge topics from first-hand research experience, along with a set of collaboratively-developed educational modules that integrate content with 2YC learning and curricula development goals.

In each year of the project, ten 2YC faculty will collaborate with CU faculty to carry out laboratory research in engineering and computer science disciplines. Example research topics include: organic and hybrid photovoltaics for renewable electric energy generation; remote sensing for precision agriculture; soft robotic manipulators for tactile sensing and robotic perception; ultrafast laser pulse experiments for infrared sensing and chemical characterization; metal nanoparticle catalysis for reduced automotive emissions and renewable material synthesis from biomass; dynamic solar windows for energy-efficient building; coherent laser sources for biomedical imaging; and organic electrochemical transistors for bioelectronic sensing and drug delivery. The 2YC faculty will come away from the immersive experience with in-depth understanding of topics of national need and at the forefront of research on areas as diverse as renewable energy, materials science, biomedical research, robotics, and other areas. In addition to advancing research in a broad array of topics while developing 2YC faculty research knowledge and skills, the project will help 2YCs to integrate their research into STEM curriculum modules specifically targeting 2YC learning goals, but focusing on ARETe research topics. Collaborative module development will be primarily driven by participating 2YC faculty, based on their research experiences at CU. The project aims to establish and cultivate learning communities to facilitate transfer of knowledge to 2YC students, rapid progression of 2YC STEM curricula, and stronger connections between CU and Colorado 2YCs. CU faculty and graduate students will provide in-person and remote support of the implementation and assessment of new curricula, including co-instruction on 2YC campuses. Research teams will follow a structured backward design approach to curriculum module development, utilizing blended and active learning to convey important modern content. As a broad-ranging goal, the cultivation of these Colorado learning communities is expected to help lower the barrier for student transfer from Colorado 2YCs to CU Engineering, through both academic preparation and social/emotional benefits from mentoring by CU faculty and graduate students.

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.