02/07/19 - 9:45 AM to 10:45 AM
Dow Lecture Series: Professor Erik Grumstrup
Dow Lecture Series
Chemical- and Structure-correlated Charge Carrier Transport in Disordered Materials
Charge carrier and exciton transport is a key parameter determining the performance of optoelectronic and electronic devices, from photovoltaics to transistors. While mobility or diffusivity are important empirical factors when comparing materials for a particular application, conventional ensemble approaches for measuring these parameters average over structural heterogeneities like grain boundaries or local crystal orientation, which are ubiquitous in the disordered materials produced through solution-based fabrication approaches. Furthermore, experimental measures of mobility often fail to link transport efficiency to intrinsic material parameters. To overcome these limitations, our group has utilized transient absorption microscopies that enable local measures of exciton or free-carrier transport to be correlated to the local material morphology as well as to material parameters like effective mass and mean scattering time. In lead halide perovskites, we have correlated direct measures of the ambipolar diffusivity to refractive index changes induced by photogenerated free charge carriers on individual perovskite domains. These optical measurements provide a local probe of how perovskite chemistry systematically determines transport rates through a tightly-coupled interplay of effective mass, band structure, and disorder.
4:30 p.m. Thursday, Feb. 7
Kate & Michael Bárány Conference Room
(117/119 Smith Hall)
“Life as a Minnesota Alum”
Research in the Professor Grumstrup's group operates at the intersection of materials science and advanced spectroscopy, where his researchers aim to address challenges associated with next-generation photovoltaic materials, nanoscale electronics, and heterogeneous catalysis. Researchers are particularly interested in photochemistry and transport processes that occur on length scales between 10 nm and 10 um, where defects, proximity to surfaces, interfacial regions, and changes in morphology are critical determiners of functionality. To characterize this “mesoscale” region, researchers develop and utilize nonlinear optical microscopies with femtosecond (~10(-15) second) temporal resolution and sub-micron (10(-6) meter) spatial resolution that allow us to watch non-equilibrium dynamics as they evolve in both space and time. They ultimately seek to understand fundamental questions of material functionality: How does charge separation occur in bulk heterojunction solar cells? Where are the active sites on nanostructured catalysts? How does electron mobility change at the interface of two material domains? Questions like these guide our group as we tackle problems in materials science, interfacial chemistry, nanoscience, and optics.
Erik Grumstrup is an alumnus of the University of Minnesota, earning his bachelor's degree in 2006. His undergraduate research adviser was Professor Kenneth Leopold. He earned his doctorate from the University of Colorado at Boulder. He was an National Resource Council Research Associate at the Army Research Office, and a post-doctoral fellow at the University of North Carolina. He has been with Montana State University since 2015.