Conjugated oligomers and polymers with functionalized side chains: tuning the pi - pi interactions and the optoelectronic properties
Final Report Abstract
In this project the electronic dynamics in side-chain-modified electron donor – acceptor oligomers are investigated. As donor functioned thiophene and thienothiophene moieties, as acceptors were used pyrrolopyrrole and fluorene entities. Ultrafast temporally resolve two-photon photoemission (2PPE) spectroscopy was employed, using a Ti:sapphire laser in the beginning and later a tunable NOPA/fiber laser for a better understanding of the processes. The side chain engineering of the organic molecules, although of great importance for the carrier mobility, has less influence on the electronic dynamics in the LUMO or LUMO-derived states. Further, the occupied states do not show a significant difference in the energetic position of states, as expected. More affected are the low-lying polaronic states, both in their energetics as well as in the electronic dynamics. It seems therefore to be important that the lifetimes in these low-lying states becomes longer, which can be achieved by single, non-branched side chains and an urea substitution within the aliphatic chain, as was hypothesized at the beginning of the project. Still ongoing and future work on this topic within our group will certainly contribute to a better understanding of the roles of these low-lying states for carrier transport. This joint project together with Deqing Zhang from ICCAS (Beijing) and originally designed for the third phase of the transregio TRR 61 Beijing – Münster “Multilevel Molecular Assemblies: Structure, Dynamics and Function” and now carried out within PAK 943, consisted of organic synthesis by our Chinese partners and electronic characterization with static and temporally resolved two-photon photoelectron spectroscopy by our group. And indeed, we found that the side chain engineering manifests itself in different low-lying polaronic states and their dynamics, as mentioned above. Such effects are difficult to investigate by only optical techniques. In this sense, we believe that we have and will further contribute to a better understanding of D – A oligomers for photovoltaic applications.
Publications
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Electron spin filtering by helical molecules. 8th International Symposium of the TRR 61 4. 10. 2018, Münster
H. Zacharias
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Electronic spin filtering by helical molecules. Int. Workshop on Dynamics, Interactions and Electronic Transitions at Surfaces (DIET 16) Eibsee, 12.10.2018
H. Zacharias
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Excited electron dynamics in thiophene-based polymers. 8th International Symposium of the TRR 61 4. 10. 2018, Münster
T. Reiker, C. Winter, D.K. Bhowmick, N.F. Kleimeier, Z. Liu, D. Zhang, H. Zacharias
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Excited electron dynamics in thiophene-based polymers. Frühjahrstagung der DPG 3. 4. 2019, Regensburg
T. Reiker, C. Winter, D.K. Bhowmick, N.F. Kleimeier, Z. Liu, D. Zhang, H. Zacharias
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Excited electron dynamics in thiophene-based polymers. Ultrafast Surface Dynamics 11 8. 6. 2019, Qiandao Lake, Zheijang, China
T. Reiker, C. Winter, D.K. Bhowmick, N.F. Kleimeier, Z. Liu, D. Zhang, H. Zacharias
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Dynamics in electronically excited states of diketopyrrolopyrrole – thiophene conjugated polymer thin films ; J. Phys. Chem. C 125, 5572 – 5580 (2021)
T. Reiker, Z. Liu, C. Winter, N.F. Kleimeier, D. Zhang, H. Zacharias
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Electronic dynamics in side-chain-engineered thiophene-based D-A organic polymers for photovoltaics. Ultrafast Surface Dynamics 12 24. 5. 2022, Benasque, Spanien
T. Reiker, D.K. Bhowmick, Z. Liu, D. Zhang, H. Zacharias
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Excited electron dynamics in thiophene-based polymers. 5th International Conference on Applied Surface Science 25. 4. 2022, Palma de Mallorca, Spanien
T. Reiker, C. Winter, D.K. Bhowmick, N.F. Kleimeier, Z. Liu, D. Zhang, H. Zacharias
