CAREER: Exploiting Open-Shell Character for Organic Optoelectronic Applications

With support from the Chemical Structure, Dynamics, and Mechanisms B Program in the Division of Chemistry and the Electronic and Photonic Materials Program in the Division of Materials Science, Dr. Mark Chen at Lehigh University will develop new carbon-based materials that exploit properties of novel molecular radicals which have unpaired electron character.

Most organic molecules only contain spin-paired electrons. This ensures environmental stability but limits the capabilities of molecular materials for optoelectronic applications. In this project, Dr.

Chen and his students are using rational design principles to construct new molecular radicals that are expected to have high environmental stability, ultimately leading to enhanced device performance when employed as luminescent and charge transport materials. The project involves a combination of chemical synthesis, followed by physical characterization studies to identify and optimize molecular structures and properties.

This interdisciplinary research facilitates the development of educational course materials, which are designed to inspire science, technology, engineering and mathematics (STEM) students to think outside the boundaries of formal disciplines. Interconnections within STEM will be promoted through outreach events aimed at recruiting student groups from the mid-Atlantic region who are underrepresented in STEM fields.

Research activities in this project are aimed at the development of new electronic materials which can exploit the effects of open-shell electronic structure. For stability, most organic molecules possess closed-shell electronic structures, where all electrons within a molecule are spin-paired. This inherently limits optoelectronic applications due to unfavorable energies related to emission mechanisms and charge transfer kinetics.

In this project, Professor Chen and his students will synthesize and systematically explore the structure-property relationships of air-stable, pi-conjugated molecules with bisphenalenyl structures that possess persistent unpaired spin. This research builds on an efficient synthetic route already developed by the Chen research group. Synthetic modifications of bisphenalenyl structures are designed to control emission wavelength and quantum efficiencies during luminescence, while also enhancing electron mobilities and conductivities during charge transport.

Research in this project is expected to impact society by introducing new optoelectronic materials and devices that are more portable, energy efficient, and less expensive to manufacture. This interdisciplinary research, which relies on chemical synthesis and diverse methods of physical characterization, provides diverse professional training opportunities for graduate and undergraduate students.

New curricula and outreach programs will inspire students to cultivate broader interests in STEM careers.

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.