Shuxia Tao

Computational Materials Physics

The Computational Materials Physics group of Shuxia Tao works on the understanding of the process-structure-property-performance relationship of materials for energy applications. To do this, we develop and use multiscale methods, combining quantum methods e.g. Density Functional Theory with classical methods e.g. Molecular Dynamics, to study the complex interplay of chemistry and physics of materials at the nanoscale.

Simulating materials one atom at a time

We use Density Functional Theory based multiscale computer simulations to design materials for energy application. Our main focus is perovskite solar cells. Perovskite solar cells have emerged as one of the most promising photovoltaic technologies because of their potentially higher efficiency and lower cost than Si ones. The one remaining challenge is the long-term stability. The state-of-the-art cells are only stable for hundreds of hours. Ion migration as well as chemical reactions are key processes causing degradation. All the above processes are triggered and accelerated by the presence of intrinsic defects in the perovskite and extrinsic device operation stress, such as, thermal stress, light excitation and electrical bias.

Multiscale Computational Method

We develop and apply multi-scale computational methods for upscaling our simulations to larger size and longer time. Our starting point is quantum mechanics (QM) method, e.g. density functional theory (DFT). Built upon our DFT expertise, we recently started exploring approximate QM method, e.g. density functional based tight binding (DFTB). Another important focus is to upscale the QM simulations to large-scale molecular dynamics (MD) simulations. To do this, we develop semi-classical reactive force field (ReaxFF) and classical force fields (CFF).

To understand the interplay of the many material properties, we combine methods used in both computational physics and computational chemistry. The materials properties we study include optoelectronic properties, thermodynamics, chemistry kinetics.

We collaborate extensively with several PIs of our department (MSM and CCER) as well as with international experts (Adri van Duin for ReaxFF) and industrial partners (SCM for DFTB and ReaxFF).

News

Fundamentals of Metal Halide Perovskites

Metal halide perovskites are a broad family of materials that exhibit wide tunability in their optoelectronic properties via composition engineering and tuning the crystal-structure dimensionality from 3D to 0D. Halide perovskites also exhibit unusual physical and chemical behaviors that are rarely seen in other materials systems.

While much of the early research focused on improving the optoelectronic properties and the best perovskite solar cells reached efficiency of about 25% in 2019. But their practical relevance remains unclear because of the instability issues of the perovskite absorber, consequently short device operation time. To enhance their long-term stability, the fundamental understanding of the physics, chemistry and materials science of these materials and devices become more critical than ever. Every bit of improvement in materials potentially translates to prolonged lifetime of the devices.

Using quantum mechanical simulations, we study the optoelectronic properties as well as the instability issues (thermal instability, ion migration, environmental factors, such as, air, light excitation).  We explore compositional engineering solutions to passivate harmful defects and we also predict physical parameters govern the reaction pathways for crystallization of perovskite film. We collaborate extensively with experimental researchers at TU/e (M2N group) as well as several international institutes.

Student opportunities

We are constantly looking for enthusiastic and bright researchers at all levels (BSc, MSc and PhD and Postdoctoral). A few examples of available projects are given here.

We also invite motivated students to discuss with the PI Shuxia Tao and our group members for the latest research projects as the field of perovskite solar cells develops fast and new exciting research questions emerge quickly.

The courses we offer are 3MN200: Computational Materials Science and 3DEX0: Physics of New Energy.

From atomistic scale to nanoscale; from static to dynamic properties

Metal halide perovskites have been the focus of many computational studies over the past few years. The bulk of these investigations were done using methods based on quantum mechanics (QM). However, the computational cost of QM methods is high, limiting the investigation of the dynamical properties, as the materials are much “softer” than traditional inorganic semiconductors.  Such softness gives rise to unusual lattice dynamics and novel behaviors. All chemical and physical properties evolve and affect one another constantly under external stimuli (heat, light, electrical bias).

To capture the complex dynamical properties, we perform molecular dynamics (MD) simulations with several levels of efficiency. Ab-initio MD based on DFT, MD base on DFTB as well as MD based on force fields. We have recently developed a set of transferable force field and successfully applied it to simulate ion migration. To be able to simulate chemistry reactions during the degradation, we have extended our effort to reactive force field (ReaxFF). On the left-hand side, phase transition of a common perovskite (CsPbI3) under thermal stress is demonstrated using our newly developed ReaxFF.

Extensive methodology development is still required. Advances in machine learning algorithms and computational power have opened the way towards accelerated force field development as well as high-throughput screening.

Meet some of our Researchers

From Materials to Devices

Perovskite solar cells have achieved an impressive power conversion efficiency of 25.2% in 2019. While its efficiency has become comparable with Si ones, their long-term stability are still far behind. Beside the perovskite absorbers, the interfaces between the perovskite and the charge transport layers are recognized as another important factor in determining both the efficiency and long-term stability.

Using DFT, we optimize energy level alignment in the whole devices, including those of charge transport layer, the perovskite absorbers, the electrodes. By tuning the composition of each layer or applying additives for surface modification, better energy alignment can be achieved. We also study the roles of defects, ion migration and redox chemistry at several interfaces in the devices.

Our long-term ambition is to apply our multiscale approach to study dynamical properties that governs the long-term stability of the devices. Our goal is to design multifunctional interfaces combining the optimal optoelectronic properties with prolonged stability. Many inspiration of our research comes from our close interactions with experimental researchers at TU/e (PMP group) and knowledge institutes and industrial partners (Solliance) . 

How TU/e technology brings the endless power of the sun to your home (and car)

The potential of solar power is enormous: our planet intercepts some 173,000 terawatts of radiation from the sun at any time, 10,000 times more power than the planet’s population uses. Harnessing this almost endless power source has been the driving force of much research at the Eindhoven University of Technology. The research covers a broad terrain of expertise and interests, ranging from the elemental building blocks of solar cells and upscaling of technology to industrial production, to enhancing the aesthetics of solar panels or application in solar-powered cars. And with success: it is estimated that almost one third of all solar cells worldwide contain technology pioneered by our researchers. We take you step by step through the whole chain: from fundamental research in the lab to the application in everyday life.

Contact

  • Visiting address

    Cascade, room 3.12
    De Zaale
    5612 AJ Eindhoven
    Netherlands
  • Postal address

    Department of Applied Physics
    P.O. Box 513
    5600 MB Einhoven
    Netherlands
  • Teamlead

    Teamlead