Principal Investigator: Petra Groß
Collaboration: Manuela Schiek, Christoph Lienau, Gunther Wittstock

Within this project we aim to observe light-induced energy transfer processes in solar cell materials with high spatial and spectral resolution. Such processes take place on nanometer length scales and femtosecond time scales in a number of functional nanostructures, but are mostly not yet fully understood. The direct, spatio-temporally resolved observation of the optical excitation of these nanostructures is thus a key enabling technique to explain the dynamics. Recently, a novel scanning near-field microscope could be demonstrated [1,2], which was shown to provide a spatial resolution of 10 nm and a temporal resolution of 10 fs [3]. Within this project, we will employ this novel, unique microscope to study energy transfer processes. As a first demonstration, we will visualize the energy- and charge transfer processes in single semiconductor-metal hybrid nanostructures. Specifically, we are interested in the strong coupling between excitons and plasmons; similar strong coupling was recently demonstrated in ensemble experiments and could be a key to the spatial transport of excitation over mesoscopic distances [4].  At the same time we will study new materials, which are currently under investigation as materials for organic solar cells, like polymer-fullerene hybrid structures (P3HT/PCBM, PPV/PCBM etc.). From optical experiments with high spatial resolution we expect to gain new information about the influence of the polymer/fullerene interface on the dynamics and the efficiency of light-induced electron transfer reactions.

1. C. Ropers, C. Neacsu, T. Elsaesser, M. Albrecht, M. Raschke, C. Lienau, Grating-coupling of surface plasmons onto metallic tips: A nanoconfined light source, Nano Lett. 7, 2784 (2007).
2. D. Sadiq, J. Shirdel, J. S. Lee, E. Selishcheva, N. Park, C. Lienau, Adiabatic Nanofocusing Scattering-Type Optical Nanoscopy of Individual Gold Nanoparticles, Nano Lett. 11,1609 (2011).
3. S. Schmidt, B. Piglosiewicz, D. Sadiq, J. Shirdel, J.S. Lee, P. Vasa, N. Park, D.-S. Kim, C. Lienau, ACS Nano 6, 6040 (2012).
4. P. Vasa, W. Wang, R. Pomraenke, M. Lammers, M. Maiuri, C. Manzoni, G. Cerullo, C. Lienau, Real-time observation of ultrafast Rabi oscillations between excitons and plasmons in metal nanostructures with J-aggregates, Nature Photonics, 7, 128-132 (2013)