Researchers at Kyushu University are blazing a trail to capitalize on SF while furthering our fundamental understanding of this fascinating process. This innovative IMPACT process could pave the way for game-changing energy conversion materials. In this most recent work, first author Gaku Fukuhara from the Institute for Materials Chemistry and Engineering led the team to synthesize a new series of SF-active molecules. These carefully crafted molecules focus on supercharging light energy amplification by using hydrostatic pressure.
Singlet fission is a truly remarkable process. In this process, a molecule splits the energy of one high-energy photon between two lower-energy excited states. This step is very important in improving the efficiency of solar energy conversion. For this project, the research team strived to build a molecule consisting of a pair of joined pentacene units using flexible polar linkers. Pentacene, an organic semiconductor molecule consisting of five fused benzene rings, acts as the starting structural unit in each of these molecules.
Despite their importance, the peculiar motif and structure of the linkers are found to be crucial in governing SF properties. These polar, flexible linkers form tunable electrical bridges between the pentacene side blades. Yet, they have a profound impact on how the molecules behave under different conditions. In the team’s experiments and computational simulations, they discovered that hydrostatic pressure could be safely and effectively used to conserve or improve control of SF photoreaction processes.
The role of hydrostatic pressure on singlet fission was found to be dependent on the solvent used during these experiments. In moderately polar solvents, e.g., in toluene, increasing the pressure leads to a decrease of SF reaction rate. Likewise, the linkers freely solvate under pressure. They help to promote such processes with their ability to facilitate singlet fission.
When changing to more polar solvents such as dichloromethane, the scientists noticed an inversion of this influence. As the pressure rose, the SF reaction rate shot up. This highlights the unique pressure–solvation dynamics dependency revealed in different environments. These triplet excitons produced via singlet fission are especially valuable because they can act swiftly and efficiently as energy carriers.
This research seeks to do more than scratch the surface. Its aim is to develop multi-functional materials that not only efficiently amplify light energy, but can be dynamically tuned through the application of pressure. These breakthroughs would enable next-generation smart applications, from phototherapeutic materials to pressure-responsive energy-conversion devices.