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Department of Physics and Astronomy Collins Research Group

Research

The physical, electronic, and kinetic properties of soft/organic matter are widely tunable and are often determined by their nano-to-mesoscale structure. The complex interplay between structure and these fundamental properties is applicable in a host of technologies and therefore important in many research areas. Unfortunately, such structure is particularly difficult to measure with many traditional probes (X-rays, neutrons, or electrons) due to their low density, similar elemental content, and poor crystallinity.

Our research explores the capabilities of resonant X-rays to explore nano-to-mesoscale physics in organic systems. Resonant X-rays probe unique molecular orbitals with the molecule allowing exquisite sensitivity to ordering in soft matter based on molecular bonds and their conformation and can even focus on ordering at buried interfaces. We focus on ordering phenomena relevant to organic electronics where much of the device function depends on the nano-to-mesoscale structure that occurs in the bulk and at interfaces. We use this novel capability to look deep inside organic systems to probe the physics of film formation and the origins of emergent optoelectronic properties of these materials in devices processed and tested in the lab.

Specific Projects are below. You also can learn more about the specific X-ray Techniques.

Connecting nano-to-mesoscale structure of organic devices to their optoelectronic properties

 

Students conduct resonant X-ray spectroscopy, microscopy and scattering to correlate domain structure, composition, crystallinity in materials systems used in high-performing organic photovoltaics and transistors to reveal the origins of high charge separation efficiencies or charge carrier mobilities.

Initially students will receive samples for X-ray investigations from collaborating groups at WSU, U of Washington, U of Potsdam (Berlin), and the National Institute of Standards and Technology

Once the laboratory is completed at WSU, students will processes their materials supplied by leading chemists into devices and measure optoelectronic properties such as solar power conversion efficiency, charge quantum efficiency, and ns laser excited transient charge generation and recombination experiments.

Example projects in this line follow similar themes as the following publications:

  • Schubert et al., Advanced Functional Materials, (2014) DOI: 10.1002/adfm.201304216b.
  • Collins et al., Advanced Energy Materials, 3, 65 (2013).
  • Collins et al., Nature Materials, 11, 536 (2012).

Exploring molecular alignment and conformation with novel resonant X-ray scattering

 

Students conduct experiments with controlled organic films and nanostructures to develop unique measurement capabilities using PISA (Polarization-Induced Scattering Anisotropy). In particular, the goal is to extract local knowledge of molecular alignment at buried interfaces, within nanostructures, or even macromolecular conformation. The ability to extract nanoscale molecular orientation and conformation is currently something not possible with any technique. The development of this capability would revolutionize how we probe organic matter.Students process specially synthesized organic molecules by collaborating chemists (e.g. U of Washington) into controlled nanostructures and measure their structure at the synchrotron using advanced scattering techniques.

Students process the scattering patterns and extract information on molecular alignment or conformation using forward simulated models including spectroscopy-based optical tensors.

  • Gann et al., Journal of Synchrotron Radiation, 23, 219, (2016).