Multidimensional photoresponsive molecular architectures for high performance solar cells

• Applicants: Professorin Dr. Cornelia Denz; Professor Dr. Nikos L. Doltsinis
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 333419941

This project aims to understand, develop, and apply optoelectronic functionalities based on the assembly of low band gap molecules into multidimensional architectures for the realization of next generation high-performance bulk heterojunction (BHJ) organic solar cells (OSCs). Our integral approach includes molecular networks of novel donors (D) and acceptors (A), photoenhanced charge transport combined with morphology control and innovative light enhancing or harvesting structures. While crucial OSC parameters as energy level matching and charge carrier mobility, studied previously, can be screened prior to fabrication, active layer morphology, which is central for optimization, is hard to predict by simple molecular structure analysis. In the upcoming project, we will exploit our previous results to perform a paradigm shift from morphology analysis to systematic morphology and architecture control combined with improved building blocks based on self-assembled networks and light-induced active layer structuring.For the inner OSC structure, we will synthesize innovative perylene bisimide A derivatives that are optimized in their functional groups allowing complex 2d and 3d structures. By effectively combining material design, synthesis, and photovoltaic evaluation, we will identify high-mobility, low-bandgap D materials, employing our original concept of enhancing the quinoid resonance of D-A materials. Synergetic A and D optimization will lead to high-performance non-fullerene OSCs.While this route will influence molecular order on the nanoscale, light-assisted processes like photo-patterning via crosslinking or photo-induced mass transfer will structure the active layer on the microscale, in constant interplay with D and A development and theoretical modeling. Patterning will not only be used to enhance charge separation and transfer, but also to generate outer light-guiding and redistributing photonic structures, e.g. aperiodic structures or surface relief gratings based on structured photopolymers, considerably improving the overall performance. Thus, we employ light as a control unit for both morphology and surface structuring and light harvesting.Multiscale modeling will provide a fundamental understanding of the relation between molecular structure and electronic properties of the D and A components and the OSC efficiency. Combining quantum-mechanical calculations with atomistic and coarse-grained molecular dynamics, we will predict the shape of self-assembled or photo-patterned networks, supporting the development of an advanced morphology. The effect of molecular mobility and stacking as well as polymer entanglement or order/disorder transitions on the overall electronic properties is studied. Thus, theory will contribute to establishing design rules for further OSC optimization.

• DFG Programme: Research Grants
• International Connection: China
• Major Instrumentation: Gloveboxsystem
• Instrumentation Group: 4670 Handschuhkästen, Schutzgasanlagen
• Cooperation Partners: Professor Dr. Yan Li; Dr. Xiaozhang Zhu