Ultrafast Spatial Imaging of Charge Dynamics in Heterogeneous Polymer Blends

• Published in: The journal of physical chemistry letters Vol. 3; no. 7; pp. 879 - 884
• Main Authors: Wong, Chris Tsz On, Lo, Shun Shang, Huang, Libai
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 05.04.2012
• Subjects: Kinetics, Spectroscopy; charge generation and recombination; organic solar cells; transient absorption microscopy; atomic force microscopy; ultrafast spectroscopy
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/jz300178g

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.