| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Energy Harvesting & Storage | Wednesday Sessions |
| Session EH-WeE |
| Session: | Characterization of Materials for Energy Applications II |
| Presenter: | Adam Schwartzberg, Lawrence Berkeley Lab, USA |
| Authors: | P. Hoffman, University of California Berkeley Y. Leblebici, University of California Berkeley A. Mathies, University of California Berkeley M. Schwartzberg, Lawrence Berkeley Lab, USA |
| Correspondent: | Click to Email |
The nature of the organic photovoltaic (OPV) bulk heterojunction interface, and how charge carriers diffuse through the individual components of this system, is of critical importance to understanding how these devices function, and how they can best be optimized. Using femtosecond stimulated Raman spectroscopy (FSRS), we have observed that in the MDMO-PPV/PCBM system there is a 150 fs time window during which excitons may propagate to the interfacial donor/acceptor region, despite the fact that the excitons persist for as much as 170 ps, greatly limiting the mobility of exciton mobility and device performance. In addition, we have found that the charge transfer region where carriers efficiently pass from donor to acceptor is approximately one monolayer wide, significantly narrower than was previously believed. This understanding is possible through the examination of electron density and chemical modifications in the molecular species which we observe using the FSRS technique in thin film samples for the first time.