Title: Interfaces in Perovskite Devices through the Lens of DFT

Speaker: Sofia Apergi (TU/e Applied Physics)
Time: June 23, 2022, 10:00–11:00
Location: Hybrid: TU/e (Flux 3.256) and online (MS Teams)

Abstract: In optoelectronic devices consisting of multiple layers of different materials, understanding the properties and phenomena that take place at surfaces and interfaces is of great importance. Such studies are quite challenging for either theory or experiment alone because the complex interplay of the materials properties is decisive for the device performance. The combination of DFT with experiments is an indispensable tool, where DFT can provide atomistic insights, which either explain experimental observations or make predictions to guide experiments. Here, several interfaces between metal halide perovskites and metal oxides present in perovskite devices will be presented. Through these examples it will be demonstrated that with DFT a variety of surface features can be derived, such as chemical reactivity, stability, and electronic properties. The observations made based on DFT results provide important information for the interpretation of experiments and materials engineering strategies to improve the functionality of these interfaces in devices.

The CCER seminars are aimed at researchers interested in computational approaches to (energy) research. The seminar is small-scale, typically 15 participants, and interactive, offering lots of room for discussion. If you would like to attend, just This email address is being protected from spambots. You need JavaScript enabled to view it..

 

 

Title: Thermodynamics of hydrogen/water systems

Speaker: Thijs Vlugt (TUD 3ME)
Time: June 2, 2022, 10:00–11:00
Location: Hybrid: TU/e (Flux 0.300) and online (MS Teams)

Abstract: Hydrogen is one of the most popular alternatives for energy storage. Because of its low volumetric energy density, hydrogen should be compressed for practical storage and transportation purposes. Recently, electrochemical hydrogen compressors (EHCs) have been developed that are capable of compressing hydrogen up to P = 1000 bar at much lower costs. As EHC compressed hydrogen is saturated with water, the maximum water content in gaseous hydrogen should meet the fuel requirements issued by the International Organization for Standardization (ISO) when refuelling fuel cell electric vehicles (< 5ppm). Knowledge on the vapor liquid equilibrium of H2O–H2 mixtures is crucial for designing a method to remove H2O from compressed H2. To the best of our knowledge, the only experimental high pressure data (P > 300 bar) for the H2O–H2 phase coexistence is from 1927 [J. Am. Chem. Soc., 1927, 49, 65–78]. Molecular simulation and thermodynamic modeling was used to study the phase coexistence and thermodynamic properties of the H2O–H2 system. Special simulations using so-called fractional molecules are needed for these simulations. It was found that the presence of water has a significant effect of the properties of compressed hydrogren, and that the water content is generally much larger than 5 ppm so that a drying step is needed. The electro osmotic drag of water inside the membrane of the electrochemical hydrogen compressor is also studied. At the end of my presentation, I present to recent cases of the use of Machine Learning (ML) in thermodynamics: (1) for the computation of partial molar properties from simulations and (2) the combination of thermodynamics and ML to solve arson cases.

The CCER seminars are aimed at researchers interested in computational approaches to (energy) research. The seminar is small-scale, typically 15 participants, and interactive, offering lots of room for discussion. If you would like to attend, just This email address is being protected from spambots. You need JavaScript enabled to view it..

 

Title: Computational studies of spintronics materials for energy-efficient electronic devices

Speaker: Jagoda Sławińska (Zernike Institute for Advanced Materials, RU Groningen)
Time: May 12, 2022, 10:00–11:00
Location: Hybrid: TU/e (Flux 1.124) and online (MS Teams)

Abstract
Materials that manifest intriguing spin-orbit-related phenomena emerge as promising candidates for the design of alternative computing devices beyond the von Neumann paradigm. In particular, the manipulation of spins via the control of material symmetries seems to be an efficient way to ensure the all-electric functioning of next-generation electronic devices, reducing power consumption.

In this talk, I will present the properties of several recently (re-)discovered materials as well as different routes of the control of spins. First, I will discuss a new type of charge-to-spin conversion revealed in chiral crystals, which is similar to chirality-induced spin selectivity occurring in molecules. This effect can manifest in chiral trigonal Te and TaSi2, where along with good efficiency of charge-to-spin conversion, the presence of the so-called persistent spin helix yields very long spin lifetimes, protecting the spins from the randomization. Such systems solve one of the important trade-offs of spintronic devices, as the large spin-orbit coupling needed for spin manipulation, does not cause spin dephasing.

Second, I will discuss the link between spin and electric polarization in ferroelectrics which can be employed in novel reconfigurable logic-in-memory units utilizing ferroelectric writing and spin-orbit readout, similarly to multiferroics. In particular, the spin-to-charge conversion in epitaxial Fe/GeTe heterostructures can be switched by an external electric field in a non-volatile way at room temperature, as shown via spin pumping experiments and rationalized by first-principles calculations. The most recent computational studies unveiled the possibility of even more efficient non-volatile electric control of spin currents in various materials, opening new routes for the design of logic-in-memory electronic devices.

  1. A. Roy, M. Guimarães, J. Sławińska, Physical Review Materials 6, 045004 (2022)
  2. A. Roy, F. Cerasoli, A. Jayaraj, K. Tenzin, M. Buongiorno Nardelli, J. Sławińska, arXiv: 2203.05518 (2022)
  3. H. Wang, P. Gopal, S. Picozzi, S. Curtarolo, M. Buongiorno Nardelli, J. Sławińska, npj Computational Materials 6 (7), 1-7 (2020)
  4. S. Varotto, L. Nessi, S. Cecchi, J. Sławińska, et al., Nature Electronics 4, 740–747 (2021)

The CCER seminars are aimed at researchers interested in computational approaches to (energy) research. The seminar is small-scale, typically 15 participants, and interactive, offering lots of room for discussion. If you would like to attend, just This email address is being protected from spambots. You need JavaScript enabled to view it..

 

Title: Excitons in halide double perovskites and the limits of the Wannier-Mott model in heterogeneous semiconductors

Speaker: Linn Leppert (UT, Computational Chemical Physics)
Time: April 21, 2022, 10:00–11:00
Location: Hybrid: TU/e (Flux 1.124) and online (MS Teams)

Abstract: Halide double perovskites are an emerging class of photoactive materials with considerable structural and electronic diversity and reliable stability towards heat and moisture under ambient conditions. However, little is known about their excitonic properties; whether simple physically motivated exciton models like the Wannier-Mott model are reliable for these quaternary, heterogeneous materials, is hard to predict a priori. In this talk I will discuss how first principles numerical modelling techniques can provide an atomistic understanding of excitons in halide double perovskites. I will show that these materials can feature a wide range of excitons, with binding energies spanning several orders of magnitude. Whether these excitons fall into the tenets of the Wannier-Mott model is determined by the symmetry and orbital character of their band edges – a consequence of their chemical heterogeneity.

The CCER seminars are aimed at researchers interested in computational approaches to (energy) research. The seminar is small-scale, typically 15 participants, and interactive, offering lots of room for discussion. If you would like to attend, just This email address is being protected from spambots. You need JavaScript enabled to view it..