Ultrafast Spatial Imaging of Charge Dynamics in Heterogeneous Polymer Blends.
Proof-of-concept transient absorption microscopy (TAM) with simultaneously high spatial and temporal resolution was demonstrated to image charge generation and recombination in model systems of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends upon extended thermal annealing. Significant spatial heterogeneity in charge generation and recombination dynamics was revealed on the length scale of hundreds of nanometers near the micrometer-sized PCBM crystallites, suggesting that information obtained in ensemble measurements by integrating over microscopically inhomogeneous areas could be misleading. In contrast to previous studies, high sensitivity of our instrumentation allows us to employ low excitation intensities to minimize higher-order recombination processes. TAM provides a unique noncontact tool to probe local functionality in microscopically heterogeneous energy harvesting systems.
†Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, United States.
Chris Tsz On
CT
Wong
‡Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.
Shun Shang
SS
Lo
†Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, United States.
Libai
L
Huang
atomic force microscopy; charge generation and recombination; organic solar cells; transient absorption microscopy; ultrafast spectroscopy