Tailoring amphiphilic organic molecules for self assembled photovoltaic materials

• Applicants: Dr. Stefan Kraner; Professor Dr. Ullrich Scherf
• Subject Area: Theoretical Chemistry: Molecules, Materials, Surfaces ; Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 419282603

• Final Report Year: 2023

Final Report Abstract

The goal of the project was to synthesize and experimentally proof the new concept of using a selfassembling amphiphilic donor-spacer-acceptor triads in organic solar cells. Both, the synthesis and the manipulation of amphiphilic molecules and its bilayer sheets is challenging. We could synthesize amphiphilic PDIs, show their well ordered bilayer sheets, and show a possible route in order to potentially extract charges by a sub-micrometer structured surface. Amphiphilic triads or dyads could not be synthesized and characterized within this project. The synthesis of amphiphilic TDIs, which is supposed to be used as a donor later on, could be synthesized. However, its poor solubility (due to the strong pi-stacking) prevents an efficient separation of chemical synthesis products (which is similar for the cyano-PDI). Therefore, more soluble submolecules or in other words, molecules with a less strong pi-stacking need to be used. However, the donor and acceptor sub-molecule in the final amphiphilic triad needs to provide a very efficient charge transport, which can be achieved beneficially with a strong pi-stacking. This contradicts each other and makes the proposed concept very difficult to be performed successful experimentally. Thus, we learned from this project that the needed amphiphilic triads are too complicated to be synthesized on a scientific level, which certainly will also hold true for commercialization. One approach to overcome the issues above is the usage of atomic layer deposited metal-oxide in combination with SAMs. A concept which needs to be investigated in more detail in future.

Publications

• Molecular design for all-in-one self-assembled donor–acceptor organic solar cells. Solar Energy Materials and Solar Cells, 244, 111798.
  Kraner, Stefan & Schmidt-Mende, Lukas
  
• “Novel concept for an optimal solar cell based on selfassembling organic molecules,” E-MRS 2023 Spring Meeting, Strasbourg, Germany, May 2023 (Oral presentation).
  S. Kraner & L. Schmidt-Mende