Carrier Multiplication: Switching Singlet Fission Through Molecular Design of Pentacene Dimers - TwoforOne2.0

• Applicant: Professor Dr. Dirk M. Guldi
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454839818

The goal of TwoforOne2.0 is to integrate molecular switches into singlet fission (SF) materials, aiming to develop a mechanism-based design that enhances light conversion efficiencies in practical solar cells to a maximum of 200% while achieving the highest attainable electromotive force. A fundamental question that underlies all device development is how to optimize molecular structures to maximize SF effectiveness. With our TwoforOne2.0 objective, we venture far beyond just proving the concept of carrier multiplication. We seek optimization through the synergies derived from ultrafast spectroscopies (such as ultrafast electronic absorption and infrared) and newly developed SF materials featuring a broad range of molecular switches. To boost power conversion efficiencies beyond the detailed balance limit, we utilize the full power of examining i-SF along the entire reaction coordinate in molecular systems. In the initial funding period, we established the fundamentals of i-SF. Our efforts have focused on using a toolbox of molecular spacers to modulated spatial orientation and fine-tune interdiabatic electronic couplings in i-SF. In the upcoming funding period, we will focus on using molecular switches to control i-SF via external stimuli through four interwoven work packages: protons, photons and electrons, and open-shell species to switch different i-SF activities on/off. Our advanced experimental studies are strategically embedded in a multidisciplinary approach with seminal contributions from synthesis, theory, and time-resolved electron paramagnetic resonance spectroscopy. Together, we aim to solve the global challenge of reaching the thermodynamic limit of energy conversion with affordable, tunable, and stable molecular materials.

• DFG Programme: Research Grants
• International Connection: Canada, USA
• Cooperation Partners: Professor Dr. Rik Tykwinski; Professor Dr. Michael R. Wasielewski
• Co-Investigator: Professorin Dr. Carolin Müller