The greatest moral and scientific challenge of our times is the climate crisis. Our group pursues research to address this crisis by creating new interfaces between basic science and applied science. In close collaboration with experimental groups, we develop complex theoretical methods for mitigating solar cell degradation, increasing solar cell efficiency, developing magnets for hybrid car engines, and inventing photovoltaic desalination.
Mitigating Solar Cell Degradation
What: Heterojunction (HJ) Si solar cells have world record efficiencies approaching 27%. However, these Si HJ solar cells have not yet been widely adopted by the market because they exhibit a performance degradation of about 1%/year, twice as high as standard cSi cells. Our group is adapting the knowledge developed via studying glassy systems to understand the leading degradation processes, with the aim of mitigating them.
How: LAMMPS molecular dynamics, Quantum Espresso DFT, Nudged Elastic Band method.
Increasing Solar Cell Efficiency
What: Our “Full Spectrum Boost Project” focuses on solar cells made of colloidal nanoparticles. Absorption is boosted at low energies by the Intermediate Band process and at high energies by Carrier Multiplication. Our cells transcend QCD: the Quantum Confinement Dilemma. Transport is modeled as ab initio-based Monte Carlo/Marcus hopping or Boltzmann theory.
How: LDA, TD-DFT, GW, BSE, Lanczos methods, Molecular Dynamics, Kinetic Monte Carlo
Magnets for Hybrid Car Engines
What: We are exploring the reversal mechanism of hard permanent magnets in order to improve their utility for alternative energy purposes. We study the competition of domain wall propagation and nucleation in sintered and nanostructured rare earth magnets. We are analyzing hard-soft composites.
How: Finite element LLG, FORC analysis: mean field + local corrections, OOMMF, analytic methods in one dimension, elastic rubber band method for barriers
What: We have invented photovoltaic desalination. We have provided the proof of concept experimentally. We are performing extensive simulations to analyze the dynamics of the desalination/flushing cycle, from the atomistic scale to simulating individual channels to building an effective medium theory for the device.
How: Finite element hydrodynamics, COMSOL hydrodynamics, effective medium theory
What: We are exploring the slow dynamics, the glassy phases and memory and aging effects of spin glasses, dislocation systems and Coulomb glasses. We also analyze the formation of avalanches and their statistics. Using scaling analysis, we research the conditions which give rise to Self Organized Criticality.
How: Parallel tempering and other accelerated Monte Carlo techniques, Scaling analysis
What: We are exploring the revolutionary memristor paradigm that promises to redefine the architecture of computers. We study the electronic transport with explicit inclusion of underlying vacancy dynamics. We treat the long range Coulomb interaction with care. We focus on the hysteretic switching phenomena and explore the role of oxide tunneling barriers
How: Molecular Dynamics, Long range interactions
Mar. 2021 Our paper "From Femtoseconds to Gigaseconds: The SolDeg Platform for the Performance Degradation Analysis of Silicon Heterojunction Solar Cells" was submitted for prominent publication.
Mar. 2021 New graduate students Zeke Zhao, Andrew Diggs, Hong Cai, Zenchao Hong, Adam Goga, and Zack Crawford all decided to join our group. Welcome to the next generation of our group!
Jan. 2021 Our group secured a large, 4 million CPU hours allocation at the National Energy Research Scientific Computing Center NERSC.
Nov. 2020 Our paper "Disordered Mott–Hubbard Physics in Nanoparticle Solids: Transitions Driven by Disorder, Interactions, and Their Interplay" was published in Nano Letters.
June 2020: Group alum Frank Wilhelm just got the position of Director of the new Institute for Quantum Computing Analytics at the German national Research lab in Jülich.
June 2020: Group alum Dustin Gilbert, an assistant professor at the University of Tennessee, also working at the Oak Ridge National Laboratory, was just awarded the prestigious CAREER award by the DOE, given to the most promising young faculty in the US.
May 2020: We have just upgraded our computational infrastructure: we acquired a cluster of 128 CPUs, housed in the UC Davis supercomputer center FARM.
May 2020: Our group was awarded a large, 2.5M CPU hour computer time allocation on the National Energy Research Scientific Computer Center for our heterojunction degradation project.
May 2020: Our group received a $600k grant from the National Science Foundation for our collaboration with Adam Moule and Matt Law on Scanning Transmission Electron Tomography of Nanoparticle Solids, with emphasis on transport.
January 2020: Our group received a $250k grant from the Solar Energies Technology Office of the DOE for our new research project to analyze the long time degradation of Si solar cells. Our theoretical effort is performed in close collaboration with the experimental group of Mariana Bertoni of Arizona State U.