The scientific goal of this IRES is to gain better understanding for the fabrication of air-stable, photon upconversion thin films or liquids that can operate efficiently with diffuse sunlight, without the need of volatile organic solvents that currently limit practical use in applications. Complete immersion in Japanese society by spending four to eight weeks in Kyushu University will provide an opportunity to experience and understand the people, traditions and culture. The cultural and scientific exposure that the U.S. students will obtain from this international collaboration will be invaluable. Kyushu University is one of the top-ranked universities in Japan, and the cosmopolitan metropolis of Fukuoka is welcoming to foreigners. This opportunity is expected to enhance the global competitiveness of the participating students in the STEM workforce, and will be made available to qualified U.S. students, especially those underrepresented in science and engineering, by broadly reaching out to the California State university system, the Univ. of California system, and students attending professional conferences organized for example, by the American Chemical Society and Materials Research Society.
In this international collaboration, four U.S. undergraduate and/ or graduate participants per year will perform fundamental research on triplet-fusion based photon upconversion both in California and Japan. The fusion of molecular excited states with triplet character is the only method for directly upconverting photons from the sun. While these high photon upconversion quantum yields have been demonstrated in volatile organic solvents, they are generally lower in thin film due to poor triplet exciton diffusion. The U.S. students will be synthesizing and fabricating liquid or thin-films of semiconductor nanocrystals and molecular emitters organized in various hosts, including proteins, organogels and surfactants, to understand and control the diffusion of photogenerated triplet excitons. This project aims to use semiconductor nanocrystals to absorb light strongly in the near-infrared wavelengths to address one of the major limitations in molecular triplet photosensitizers. The hybrid nanomaterials will be designed to halt the spontaneous crystallization of the molecular emitter with nitrene crosslinking chemistry; increase triplet diffusion lengths in liquids or thin films with long-range order in covalent organic frameworks and establish a barrier to oxygen to prevent the quenching of spin-triplet excitons.
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.
