Chad Risko

  • Assistant Professor
  • Chemistry
  • Materials
  • Physical
276 CAER Laboratory 2, 217 Chemistry-Physics Building
859-257-0438
Research Interests:
Education

B.S. Baker University, Baldwin City, KS, 1998
Ph.D. Georgia Institute of Technology, Atlanta, GA, 2005

Research

Our research group, through the development and implementation of theoretical materials chemistry approaches, uncovers critical relationships among molecular composition, packing, and the resulting electronic, redox, and optical properties of novel materials of interest for energy conversion and storage applications & new generations of electronic and optoelectronic devices. We seek to derive an integrated understanding of how chemical structure, interactions at materials interfaces, and external stimuli drive molecular assembly over multiple length and time scales, and how the nature of these assemblies influence the subsequent electron- and energy-transfer processes that are key to material performance.

In our program, we use a wide range of computational chemistry methods – including electronic-structure methods, atomistic molecular dynamics (MD) simulations, and coarse-grained (CG) techniques – and models derived from condensed-matter physics to span the hierarchical nature of the materials under study. Such a multiscale approach is required as the problem complexity ranges from needing to describe the nature and strength of the non-covalent forces that energetically drive molecular conformations and packing through the dynamic and often kinetically controlled assembly processes to the final materials-scale properties of experimental and device relevance.

An ultimate goal of our studies is to guide and accelerate materials development by using the molecular- and nano-scale details that arise from the theoretical investigations to tailor structures in silico and transform these systems, in multidisciplinary collaboration with synthetic and materials scientists and device engineers, into engineered materials with controlled function.

Graduate Training

Theoretical Materials Chemistry

Selected Publications: 

On the Impact of Isomer Structure and Packing Disorder in Thienoacene Organic Semiconductors. Thorley, K.J. & Risko, C. Journal of Materials Chemistry C, 4, 4040-4048 (2016).

Mapping the Configuration Dependence of Electronic Coupling in Organic Semiconductors. Thorley, K.J. & Risko, C. Journal of Materials Chemistry C, 4, 3825-3832 (2016).

Overcharge Protection Above 4 V with Phenothiazine Redox Shuttles. Kaur, A.P., Casselman, M.D., Elliott, C.F., Parkin, S.R., Risko, C. & Odom, S.A. Journal of Materials Chemistry A, 4, 5410-5414 (2016).

Noncovalent Interactions and Impact of Charge Penetration Effects in Linear Oligoacene Dimers and Single Crystals. Ryno, S., Risko, C. & Brédas, J.L. Chemistry of Materials, 28, 3990-4000 (2016).

Non-Covalent Intermolecular Interactions in Organic Electronic Materials: Implications for Molecular Packing vs. Electronic Properties. Sutton, C.S., Risko, C. & Brédas, J.L. Chemistry of Materials, 28, 3-16 (2016).

Dynamics, Miscibility, and Morphology in Polymer:Molecule Blends: The Impact of Chemical Functionality. Do, K., Risko, C., Anthony, J.E., Amassian, A. & Brédas, J.L. Chemistry of Materials, 27, 7643-7651 (2015).

Dimers of Nineteen-Electron Sandwich Compounds: An Electrochemical Study of the Kinetics of their Formation. Moudgil, K., Mann, M., Risko, C., Bottomley, L.A., Marder, S.R. & Barlow, S. Organometallics, 34, 3706-3712 (2015).

Rubrene: The Interplay Between Intramolecular and Intermolecular Interactions Determines the Planarization of its Tetracene Core in the Solid State.Sutton, C., Marshall, M.S., Sherill, C.D., Risko, C. & Brédas, J.L. Journal of the American Chemical Society, 137, 8775-8782 (2015).

A Molecular-Scale Understanding of Cohesion and Fracture in P3HT:Fullerene Blends. Tummala, N.R., Bruner, C., Risko, C., Brédas, J.L. & Dauskardt, R.H. ACS Applied Materials and Interfaces, 7, 9957-9964 (2015).

The Fate of Phenothiazine-based Redox Shuttles in Lithium Ion Batteries. Casselman, M.D., Kaur, A.P., Narayana, K.A., Elliott, C.F., Risko, C. & Odom, S.A. Physical Chemistry Chemical Physics, 17, 6905-6912 (2015).

N-Substituted Phenothiazine Derivatives: How Stability of the Neutral and Radical Cation Forms Affect Overcharge Performance in Lithium-Ion Batteries. Narayana, K.A., Casselman, M.D., Elliott, C.F., Ergun, S., Parkin, S.R., Risko, C. & Odom, S.A. ChemPhysChem (2015), ChemPhysChem 16, 1179-1189 (2015).

Influence of Molecular Shape on Solid-State Packing in Disordered PC61BM and PC71BM Fullerenes. Williams, M., Tummala, N.R., Aziz, S.G., Risko, C. & Brédas J.L. Journal of Physical Chemistry Letters, 5, 3427-3433 (2014).

Structure and Disorder in Squaraine-C60 Organic Solar Cells: A Theoretical Description of Molecular Packing and Electronic Coupling at the Donor-Acceptor Interface. Fu, Y.T., da Silva Filho, D.A., Sini, G., Asiri, A.M., Aziz, S.G., Risko, C. & Brédas, J.L. Advanced Functional Materials, 24, 3790-3798 (2014).

Impact of Molecular Packing on Electronic Polarization in Organic Crystals: The Case of Pentacene vs. TIPS-Pentacene. Ryno, S., Risko, C. & Brédas, J.L. Journal of the American Chemical Society, 136, 6421-6427 (2014).

Substrate-Induced Variations of Molecular Packing, Dynamics, and Intermolecular Electronic Couplings in Pentacene Monolayers on the Amorphous Silica Dielectric. Viani, L., Risko, C., Toney, M.F., Breiby, D.W. & Brédas, J.L. ACS Nano, 8, 690-700 (2014).

Materials-Scale Implications of Solvent and Temperature on [6,6]-Phenyl-C61-Butyric Acid Methyl Ester (PCBM): A Theoretical Perspective. Tummala, N.R., Mehraeen, S., Fu, Y.T., Risko, C. & Brédas, J.L. Advanced Functional Materials, 23, 5800-5813 (2013).

Intermixing at the Pentacene-Fullerene Bilayer Interface: A Molecular Dynamics Study. Fu, Y.T., Risko, C. & Brédas, J.L. Advanced Materials, 25, 878–882 (2013).

Use of X-ray Diffraction, Molecular Simulations, and Spectroscopy to Determine the Molecular Packing in a Polymer-Fullerene Bimolecular Crystal. Cates Miller, N., Cho, E., Junk, M.J.N., Gysel, R., Risko, C., Kim, D., Sweetnam, S., Miller, C.E., Richter, L.J., Kline, R.J., Heeney, M., McCulloch, I., Zhao, K., Graham, K.R., Amassian, A., Acevedo-Feliz, D., Knox, C., Hansen, M.R., Dudenko, D., Chmelka, B.F., Toney, M.F., Brédas, J.L. & McGehee, M.D. Advanced Materials, 45, 6071–6079 (2012).

Unification of Trap-Limited Electron Transport in Semiconducting Polymers. Nicolai, H. T., Kuik, M., Wetzelaer, G. A. H., de Boer, B., Blom, P. W. M., Campbell, C., Risko, C. & Brédas, J.L. Nature Materials, 11, 882-887 (2012).

The Three-Dimensional Packing Structure and Electronic Properties of Biaxially-Oriented Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) Films. Cho, E., Risko, C., Kim, D., Gysel, R., Miller, N.C., Breiby, D.W., McGehee, M.D., Toney, M.F., Kline, R.J. & Brédas, J.L. Journal of the American Chemical Society, 134, 6177–6190 (2012).

A Quantum-Chemical Perspective into Low Optical-Gap Polymers for Highly Efficient Organic Solar Cells. Risko, C., McGehee, M.D. & Brédas, J.L. Chemical Science 2, 1200-1218 (2011).

Fullerene–Carbene Lewis Acid–Base Adducts. Li, H., Risko, C., Seo, J.H., Campbell, C., Wu, G., Brédas, J.L. & Bazan, G.C. Journal of the American Chemical Society 133, 12410-12413 (2011).

Transition from Tunneling to Hopping Transport in Long, Conjugated Oligo-imine Wires Connected to Metals. Choi, S.H., Risko, C., Delgado, M.C.R., Kim, B., Brédas, J.L. & Frisbie, C.D. Journal of the American Chemical Society 132, 4358-4368 (2010).

Synthesis, and Characterization of Ladder-Type Molecules and Polymers. Air-Stable, Solution-Processable n-Channel and Ambipolar Semiconductors for Thin-Film Transistors via Experiment and Theory. Usta, H., Risko, C., Wang, Z. M., Huang, H., Deliomeroglu, M.K., Zhukhovitskiy, A., Facchetti, A. & Marks, T.J. Design, Journal of the American Chemical Society 131, 5586-5608 (2009).

Experimental and Theoretical Identification of Valence Energy Levels and Interface Dipole Trends for a Family of (Oligo)phenylene-ethynylenethiols Adsorbed on Gold. Risko, C., Zangmeister, C.D., Yao, Y., Marks, T.J., Tour, J.M., Ratner, M.A. & van Zee, R.D. Journal of Physical Chemistry C 112, 13215-13225 (2008).

Synthesis, Characterization, and Transistor Response of Semiconducting Silole Polymers with Substantial Hole Mobility and Air Stability. Experiment and Theory. Lu, G., Usta, H., Risko, C., Wang, L., Facchetti, A., Ratner, M. A. & Marks, T. J. Journal of the American Chemical Society 130, 7670-7685 (2008).

Charge Transport through Oligoarylene Self-Assembled Monolayers: Interplay of Molecular Organization, Metal-Molecule Interactions, and Electronic Structure. Grave, C., Risko, C., Shaporenko, A., Wang, Y. L., Nuckolls, C., Ratner, M. A., Rampi, M. A. & Zharnikov, M. Advanced Functional Materials 17, 3816-3828 (2007).

Electron Affinities of 1,1-diaryl-2,3,4,5-tetraphenyisiloles: Direct Measurements and Comparison with Experimental and Theoretical Estimates. Zhan, X. W., Risko, C., Amy, F., Chan, C., Zhao, W., Barlow, S., Kahn, A., Brédas, J.L. & Marder, S.R. Journal of the American Chemical Society 127, 9021-9029 (2005).

Intervalence Transitions in the Mixed-Valence Monocations of Bis(triarylamines) Linked with Vinylene and Phenylene-Vinylene Bridges. Barlow, S., Risko, C., Chung, S. J., Tucker, N. M., Coropceanu, V., Jones, S. C., Levi, Z., Brédas, J.L. & Marder, S.R. Journal of the American Chemical Society 127, 16900-16911 (2005).

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