CAREER: Stretchable Light-Emitting Polymers with Thermally Activated Delayed Fluorescence

University Of Chicago, Chicago IL

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY For human-integrated wearable and implantable electronics, light-emitting devices (such as organic light-emitting diodes, OLEDs) play important roles for applications such as displays, light-based vital-sign monitoring and disease therapy, bio-imaging, and optical bio-stimulation of cell activities. For these devices to have conformable skin/tissue contacts and long-term compatibility, one of the key requirements is to have tissue-like mechanical stretchability. However, all the high-performance light-emitting inorganic and organic materials available so far are relatively rigid and brittle. This research will develop and study a new class of polymers that combines high-efficiency light-emitting mechanisms with rubber-like mechanical properties. These new polymers will be created through both the chemical synthesis of new structures and the physical engineering of existing chemical structures. Through fundamental studies on the influence of different rubbery designs on light-emitting performance, this research will provide design principles for this new class of polymers for achieving both high efficiency in light-emitting devices and high stretchability. Enabled by this research, the stretchable light-emitting technology could impact the emerging areas of precision healthcare, human-machine interactions, and artificial intelligence. This research will enrich the education and training for graduate and undergraduate students, as well as promote the participation of underrepresented minority (URM) students in STEM research through partnerships with high schools and the Museum of Science and Industry in Chicago's South Side. PART 2: TECHNICAL SUMMARY Stretchable light-emitting devices represent an important component in the emerging area of human-integrated electronics that are desired to achieve skin/tissue-like mechanical properties and biocompatibility. However, for electroluminescent properties, the realization and understanding of the impacts of incorporating mechanically stretchable molecular designs on photophysical behaviors remain rare. This research aims to create a set of material design principles for integrating strain-dissipation mechanisms into a state-of-the-art category of light-emitting materials, that is "thermally activated delayed fluorescence" (TADF) polymers, so as to combine skin-like stretchability with high electroluminescence efficiencies. Specifically, this research will explore and study four general approaches for imparting stretchability onto TADF polymers: 1) chemically modulating the flexibility of polymer backbones; 2) chemically building flexibility onto polymer side chains; 3) physically loosening the interchain packing and interaction; 4) imparting stretchability onto “host” polymers for TADF emitters. Enabled by the new polymer designs from these four approaches, this research will carry out fundamental studies on the structure-property relationships that combine thermodynamic, mechanical, and electroluminescent aspects for TADF polymers by combining multi-aspect experimental characterizations and theoretical simulations. This research will also develop the future workforce at both undergraduate and graduate levels, with special relevance to for the emerging wearable and implantable electronics industry. The PI will also develop a new program for bringing STEM research to high school students in Chicago's South Side which have a high proportion of underrepresented minorities, as well as the development of scientific exhibits and public lectures for the “Museum of Science and Industry, Chicago”. 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.