C. G. Bischak, C. L. Hetherington, Z. Wang, J. T. Precht, D. M. Kaz, D. G. Schlom, N. S. Ginsberg. "Cathodoluminescence-activated nano-imaging: Non-invasive near-field scanning optical microscopy with no moving parts," submitted (2015).
C. Y. Wong, B. L. Cotts, H. Wu, N. S. Ginsberg. “Exciton dynamics reveal aggregates with intermolecular order at hidden interfaces in solution-cast organic semiconducting films,” Nature Communications, 6, 5946 (2015).

Large-scale organic electronics manufacturing requires solution processing. For small-molecule organic semiconductors, solution processing results in crystalline domains with high charge mobility, but the interfaces between these domains impede charge transport, degrading device performance. Although understanding these interfaces is essential to improve device performance, their intermolecular and electronic structure is unknown: they are smaller than the diffraction limit, are hidden from surface probe techniques, and their nanoscale heterogeneity is not typically resolved using X-ray methods. Here we use transient absorption microscopy to isolate a unique signature of a hidden interface in a ​TIPS-pentacene thin film, exposing its exciton dynamics and intermolecular structure. Surprisingly, instead of finding an abrupt grain boundary, we reveal that the interface can be composed of nanoscale crystallites interleaved by a web of interfaces that compound decreases in charge mobility. Our novel approach provides critical missing information on interface morphology necessary to correlate solution-processing methods to optimal device performance. doi link PDF

S. Sharifzadeh, C. Y. Wong, H. Wu, B. L. Cotts, N. S. Ginsberg, and J. B. Neaton. "Relating the physical structure and optoelectronic function of crystalline TIPS-pentacene," Advanced Functional Materials (2014).

Theory and experiment are combined to investigate the nature of low-energy excitons within ordered domains of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) polycrystalline thin films. First-principles density functional theory and many-body perturbation theory calculations, along with polarization-dependent optical absorption spectro-microscopy on ordered domains, show multiple low-energy absorption peaks that are composed of excitonic states delocalized over several molecules. While the first absorption peak is composed of a single excitonic transition and retains the polarization-dependent behavior of the molecule, higher energy peaks are composed of multiple transitions with optical properties that can not be described by those of the molecule. The predicted structure-dependence of polarization-dependent absorption reveals the exact inter-grain orientation within the TIPS-PEN film. Additionally, the degree of exciton delocalization can be significantly tuned by modest changes in the solid-state structure and the spatial extent of the excitations along a given direction is correlated with the degree of electronic dispersion along the same direction. These findings pave the way for tailoring the singlet fission efficiency of organic crystals by solid-state structure. doi link PDF

D. M. Kaz, C. G. Bischak, C. L. Hetherington, H. H. Howard, X. Marti, J. D. Clarkson, C. Adamo, D. G. Schlom, R. Ramesh, S. Aloni, D. F. Ogletree, N. S. Ginsberg. “Bright Cathodoluminescent Thin Films for Scanning Nano-Optical Excitation and Imaging,” ACS Nano, 7, 10397-10404 (2013).


Demand for visualizing nanoscale dynamics in biological and advanced materials continues to drive the development of subdiffraction optical probes. While many strategies employ scanning tips for this purpose, we instead exploit a focused electron beam to create scannable nanoscale optical excitations in an epitaxially grown thin-film of cerium-doped yttrium aluminum perovskite, whose cathodoluminescence response is bright, robust, and spatially resolved to 18 nm. We also demonstrate lithographic patterning of the film’s luminescence at the nanoscale. We anticipate that converting these films into free-standing membranes will yield a powerful near-field optical microscopy without the complication of mechanical scanning. doi link PDF

C. Y. Wong, S. B. Penwell, B. L. Cotts, R. Noriega, H. Wu, N. S. Ginsberg. “Revealing Exciton Dynamics in a Small-Molecule Organic Semiconducting Film with Subdomain Transient Absorption Microscopy.” Journal of Physical Chemistry C, 117, 22111-22122 (2013).

The ultrafast spectroscopy of single domains of polycrystalline films of TIPS-pentacene, a small-molecule organic semiconductor of interest in electronic and photovoltaic applications, is investigated using transient absorption microscopy. Individual domains are distinguished by their different polarization-dependent linear and nonlinear optical responses. As compared to bulk measurements, we show that the nonlinear response within a given domain can be tied more concretely to specific physical processes that transfer exciton populations between specified electronic states. By use of this approach and a simple kinetic model, the signatures of singlet fission as well as vibrational relaxation of the initially excited singlet state are identified. As such, observing exciton dynamics within and comparing exciton dynamics between different TIPS-pentacene domains reveal the relationship between photophysics and film morphology needed to improve device performance. doi link PDF


Professor Ginsberg's Previous Work:

G. S. Schlau-Cohen, A. Ishizaki, T. R. Calhoun, N. S. Ginsberg, M. Ballottari, R. Bassi, and G. R. Fleming. “Elucidation of the timescales and origins of quantum electronic coherence in LHCII,” Nature Chemistry, 4, 389 (2012). doi link

N. S. Ginsberg, J. D. Davis, M. Ballottari, Y.-C. Cheng, R. Bassi, and G. R. Fleming. “Solving structure in the CP29 light harvesting complex with polarization-phased 2D electronic spectroscopy,” Proceedings of the National Academy of Science, 108, 3848-3853 (2011). doi link

G. S. Schlau-Cohen, T. R. Calhoun, N. S. Ginsberg, M. Ballottari, R. Bassi, G. R. Fleming. “Spectroscopic Elucidation of Uncoupled Transition Energies in the Major Photosynthetic Light Harvesting Complex, LHCII,” Proceedings of the National Academy of Science, 107, 13276 (2010). doi link

T. R. Calhoun, N. S. Ginsberg, G. S. Schlau-Cohen, Y-C. Cheng, M. Ballottari, R. Bassi, and G. R. Fleming. “Quantum Coherence Enabled Determination of the Energy Landscape in Light Harvesting Complex II,” Journal of Physical Chemistry B, 113, 16291 (2009). (cover article). doi link

G. S. Schlau-Cohen, T. R. Calhoun, N. S. Ginsberg, E. L. Read, M. Ballottari, R. Bassi, G. R. Fleming. “Mapping Pathways of Energy Flow in LHCII with Two-Dimensional Electronic Spectroscopy,” Journal of Physical Chemistry B, 113, 15352 (2009). doi link

N. S. Ginsberg, Y.-C. Cheng, and G. R. Fleming. “Two-dimensional electronic spectroscopy of molecular aggregates,” Accounts of Chemical Research 42, 1352 (2009). doi link

N. S. Ginsberg, S. R. Garner, L. V. Hau. “Coherent control of optical information with matter wave dynamics,” Nature 445, 623 (2007). doi link,
- cover article; featured in New York Times, National Public Radio, Nature video stream and podcast

C. Slowe, N. S. Ginsberg, T. Ristroph, A. Goodsell, L. V. Hau. “Ultraslow Light & Bose-Einstein Condensates: Two-way Control with Coherent Light & Atom Fields,” Optics & Photonics News 16, 30 (2005). doi link

N. S. Ginsberg, J. Brand, L. V. Hau. “Observation of Hybrid Soliton Vortex-Ring Structures in Bose-Einstein Condensates,” Physical Review Letters 94, 040403 (2005). doi link
- highlighted in American Institute of Physics’ “Physics News Update,” Physics Today’s “Physics Update,” and selected as one of 44 articles from 2005 to be highlighted in APS News, February 2006

Z. Dutton, N. S. Ginsberg, C. Slowe, L. V. Hau. “The Art of Taming Light: Ultra-slow and Stopped Light,” Europhysics News 35, 33 (2004). doi link

D. I. Hoult, N. S. Ginsberg. “The Quantum Origins of the Free Induction Decay Signal and Spin Noise,” Journal of Magnetic Resonance 148, 182 (2001). doi link