Research

Solving Bethe-Salpeter Equations (BSE) without explicit empty electronic states and including spin, electron and lattice couplings

Optoelectronic and spin-optotronic properties of low dimentional materials including many body interactions

Low dimentional materials including (quantum dots, nanowires/nanotubes, 2D materials) have highly tunable optical properties and stronger electron hole interactions comparing with 3D materials. We solve Bethe-Salpeter Equations (BSE) without explicit empty electronic states to treat e-h interactions explicitly and optimize their optical properties by forming interfaces, introducing defects and surface functionalization. We study spin-defects in 2D materials for quantum information applications, focusing on their excited state lifetime and spin relaxation/decoherence mechanism.  We develop charge correction schemes that can provide reliable charged defect properties for 2D systems and general interfaces, exciton radiative and nonradiative recombination rates through electron-phonon couplings, and spin-lattice relaxation time through first-principles.

Representative papers:

“Dimensionality and Anisotropicity Dependence of Radiative Recombination in Nanostructured Phosphorene”, Feng Wu, Dario Rocca, and Yuan Ping, Journal of Materials Chemistry C (Emerging Investigators themed issue), accepted, 2019, preprint: http://arxiv.org/abs/1903.11773

First-principles Engineering of Charged Defects for Two-dimensional Quantum Technologies”,  W. Feng, A. Galatas, R. Sundararaman, D. Rocca and Y. Ping, Physical Review Materials (Rapid Communication), 1, 071001(R) (2017),  https://arxiv.org/abs/1710.00257

Spin-optotronic Properties of Organo-metal Halide Perovskites”, Yuan Ping and Jin Zhang, Journal of Physical Chemistry Letters9, 5906, (2018) (journal cover).

“Electronic Excitations in Light Absorbers for Photoelectrochemical Energy Conversion: First Principles Calculations Based on Many Body Perturbation Theory”, Y. Ping, D. Rocca and G. Galli, Chemical Society Reviews, 42, 2437, (2013).

“Ab-initio Calculations of Absorption Spectra of Semiconducting Nanowires within Many Body Perturbation Theory”, Y. Ping, D. Rocca, D. Lu and G. Galli, Physical Review B, 85, 035316, (2012).

“Bethe-Salpeter Equation Without Empty Electronic States: Application to Bulk Systems”, D. Rocca, Y. Ping, G. Galli, Physical Review B, 85, 045116, (2012).

Improving optical and carrier transport properties by computational desigin

Defects or doping effects on transition metal oxides

Defects and doping can significantly modify the electronic structure, optical and carrier transport properties of transition metal oxides (TMOs). We coupled the Landau-Zener theory extended to non-adiabatic electron transfer with kinetic Monte Carlo samplings to compute small polaron hopping mobility in doped TMOs, understand polaron-defect interactions and identify dopants that can boost polaronic conduction in TMOs.

Representative Papers:

Combining Landau-Zener Theory and Kinetic Monte Carlo Sampling for Small Polaron Mobility of Doped BiVO4 from First-principles”, Feng Wu and Yuan Ping, Journal of Materials Chemistry A,  6, 20025-20036 (2018).  arXiv:1808.02507

Mechanistic Insights of Enhanced Spin Polaron Conduction in CuO through Atomic Doping”, Tyler Smart, Allison Cardiel, Feng Wu, Kyoung-Shin Choi and Yuan Ping, npj Computational Materials4, 61 (2018).

“Simultaneous Enhancements in Photon Absorption and Charge Transport of BiVO4 Photoanodes for Solar Water Splitting”, T. Kim, Y. Ping, G. Galli and K. Choi, Nature Communications, 6, 8769, (2015). (Highlighted in News of University of Chicago)

“Thermally Stable N2-intercalated WO3 Photoanodes for Water Oxidation, Q. Mi, Y. Ping, Y. Li, B. Brunschwig, G. Galli, H. Gray and N. Lewis, Journal of the American Chemical Society, 134, 18318, (2012). (Highlighted in the feature article of CCI Solar)

“Synthesis, Photoelectrochemical Properties, and First Principle Study of n-type CuW1-xMoxO4 Electrodes Showing Enhanced Visible Light Absorption”, J. Hill, Y. Ping, G. Galli, K. Choi, Energy & Environmental Science (Communication), 6, 2440, (2013).

Using DFT and GW approximations for the band alignment, charge transfer and catalytic properties

Charge transfer and catalytic properties at complex solid-liquid interfaces

Charge transfer and catalytic reactions at solid-liquid interfaces are important for solar-to-fuel, fuel cell and battery applications. We use DFT and GW approximations for the band alignment and charge transfer at the solid-liquid interfaces with implicit or explicit solvents; furthermore, we study surface catalytic reaction mechanisms including thermodynamic reaction free energies, kinetic barriers and reaction rates at the constant potential condition, directly comparing with experimental electrochemical Tafel plots and overpotential measurements.

Representative papers:

Modeling Heterogeneous Interfaces for Solar Water Splitting, T. Pham, Y. Ping and G.Galli, Nature Materials, 16, 401–408 (2017) 

“Energetics and Solvation Effects at the Photoanode/Catalyst Interface:Ohmic Contact versus Schottky Barrier”, Y. Ping, W. Goddard III and G.Galli, Journal of the American Chemical Society, 137, 5264, (2015).

“Solvation Effect on Band Edge Positions of Photocatalysts from First Principles”, Y. Ping, R. Sundararaman, and W. Goddard III, Physical Chemistry Chemical Physics, 17, 30499, (2015). (Highlighted in the feature article of Joint Center for Artificial Photosynthesis)

“The Reaction Mechnism with Free Energy Barriers at Constant Potentials for the Oxygen Evolution Reaction at IrO2(110) Surface”, Y. Ping, R. Nielsen, W. Goddard III, Journal of the American Chemical Society139, 149-155, (2017).