Computational Physics and Materials Science (CPMS)

Permanent URI for this collection

For more information visit: http://cpms.kaust.edu.sa/Pages/Home.aspx

Browse

Recent Submissions

Now showing 1 - 5 of 542
  • Article

    Potential of AlP and GaN as barriers in magnetic tunnel junctions.

    (2023-09-13) Shukla, Gokaran; Abdullah, H. M.; Schwingenschlögl, Udo; Physical Science and Engineering (PSE) Division; Material Science and Engineering Program; Applied Physics; KAUST Solar Center (KSC)

    AlP and GaN are wide band gap semiconductors used industrially in light emitting diodes. We investigate their potential as tunnel barriers in magnetic tunnel junctions, employing density functional theory and the non-equilibrium Green's function method for ground state and quantum transport calculations, respectively. We show that the valence band edges are dominated by pz orbitals and the conduction band edges are dominated by s orbitals. Both materials filter Bloch states of Δ1 symmetry at the Γ-point of the Brillouin zone. In the zero bias limit, we find for the Co/AlP/Co junction a high tunnel magnetoresistance of ∼200% at the Fermi energy and for the Co/GaN/Co junction a tunnel magnetoresistance of even ∼300% about 1.4 eV below the Fermi energy.

  • Preprint

    Stable Organic Solar Cells Enabled by Interlayer Engineering

    (Authorea, Inc., 2023-09-11) Hadmojo, Wisnu Tantyo; Isikgor, Furkan Halis; Lin, Yuanbao; Ling, Zhaoheng; He, Qiao; Faber, Hendrik; Yengel, Emre; Ali, Roshan; Samad, Abdus; Ardhi, Ryanda Enggar Anugrah; Jeong, Sang; Woo, Han Young; Schwingenschlögl, Udo; Heeney, Martin; Anthopoulos, Thomas D.; King Abdullah University of Science and Technology KAUST Solar Research Center; KAUST Solar Center (KSC); Physical Science and Engineering (PSE) Division; Material Science and Engineering Program; Applied Physics; Chemical Science Program; Imperial College London; Korea University

    The development of high-performance organic solar cells (OSCs) with high operational stability is essential to accelerate their commercialization. Unfortunately, there is currently a lack of detailed understanding of the origin of instabilities in state-of-the-art OSCs based on bulk heterojunction (BHJ) featuring non-fullerene acceptors (NFAs). Herein, we developed NFA-based OSCs using different charge extraction interlayer materials and studied their storage, thermal, and operational stabilities. Despite the high power conversion efficiency (PCE) of the OSCs (17.54%), we found that cells featuring self-assembled monolayers (SAMs) as hole-extraction interlayers exhibited poor stability. The time required for these OSCs to reach 80% of their initial performance (T80) was only 6 h under continuous thermal stress at 85 °C in a nitrogen atmosphere and 1 h under maximum power point tracking (MPPT) in a vacuum. Inserting MoOx between ITO and SAM enhanced the T80 to 50 h and ~15 h after the thermal and operational stability tests, respectively, while maintaining a PCE of 16.9%. Replacing the organic PDINN electron transport layer with ZnO NPs further enhances the cells’ thermal and operational stability, boosting the T80 to 1000 and 170 h, respectively. Our work reveals the synergistic role of charge interlayers and device architecture in developing efficient and stable OSCs.

  • Article

    Ferromagnetism and ferroelectricity in a superlattice of antiferromagnetic perovskite oxides without ferroelectric polarization

    (Springer Science and Business Media LLC, 2023-09-07) Rout, Paresh Chandra; Ray, Avijeet; Schwingenschlögl, Udo; Physical Science and Engineering (PSE) Division; Material Science and Engineering Program; Applied Physics; KAUST Solar Center (KSC)

    We study the structural, electronic, and magnetic properties of the SrCrO3/YCrO3 superlattice and their dependence on epitaxial strain. We discover that the superlattice adopts A-type antiferromagnetic (A-AFM) ordering in contrast to its constituents (SrCrO3: C-AFM; YCrO3: G-AFM) and retains it under compressive strain while becoming ferromagnetic (5 μB per formula unit) at +1% strain. The obtained ferroelectric polarization is significantly higher than that of the R2NiMnO6/La2NiMnO6 (R = Ce to Er) series of superlattices [Nat. Commun. 5, 4021 (2014)] due to a large difference between the antipolar displacements of the Sr and Y cations. The superlattice is a hybrid-improper multiferroic material with a spontaneous ferroelectric polarization (13.5 μC/cm2) approaching that of bulk BaTiO3 (19 μC/cm2). The combination of ferromagnetism with ferroelectricity enables multistate memory applications. In addition, the charge-order-driven p-type semiconducting state of the ferromagnetic phase (despite the metallic nature of SrCrO3) is a rare property and interesting for spintronics. Monte Carlo simulations demonstrate a magnetic critical temperature of 90 K for the A-AFM phase without strain and of 115 K for the ferromagnetic phase at +5% strain, for example.

  • Article

    Bandgap Engineering of Melon Using Highly Reduced Graphene Oxide for Enhanced Photoelectrochemical Hydrogen Evolution

    (Wiley, 2023-08-07) Ashraf, Muhammad; Ali, Roshan; Khan, Ibrahim; Ullah, Nisar; Ahmad, Muhammad Sohail; Kida, Tetsuya; Wooh, Sanghyuk; Tremel, Wolfgang; Schwingenschlögl, Udo; Tahir, Muhammad Nawaz; Physical Science and Engineering Division (PSE) King Abdullah University of Science and Technology (KAUST) Thuwal 23955–6900 Saudi Arabia; Physical Science and Engineering (PSE) Division; Material Science and Engineering Program; Applied Physics; KAUST Solar Center (KSC); Chemistry Department King Fahd University of Petroleum & Minerals Dharan 31261 Kingdom of Saudi Arabia; School of Chemical Engineering and Materials Science Chung-Ang University 84 Heukseok-ro, Dongjak-gu Seoul 06974 Republic of Korea; Department of Advanced Science and Technology Kumamoto University 2-39-1 Kurokami, Chuo-ku Kumamoto 860–8555 Japan; Chemistry Department Johannes Gutenberg-University Duesbergweg 10–14 D-55128 Mainz Germany; Interdisciplinary Research Center for Hydrogen and Energy Storage King Fahd University of Petroleum & Minerals Dhahran 31261 Saudi Arabia

    The uncondensed form of polymeric carbon nitrides (PCN), generally known as melon, is a stacked two-dimensional structure of poly(aminoimino)heptazine. Melon is used as a photocatalyst in solar energy conversion applications, but suffers from a poor photoconversion efficiency due to weak optical absorption in the visible spectrum, high activation energy, and inefficient separation of photoexcited charge carriers. We report experimental and theoretical studies to engineer the bandgap of melon with highly reduced graphene oxide (HRG). Three HRG@melon nanocomposites with different HRG:melon ratios (0.5%, 1%, and 2%) were prepared. The 1% HRG@melon nanocomposite showed a higher photocurrent density (71 μA cm−2) than melon (24 μA cm−2) in alkaline conditions. The addition of a hole scavenger further increased the photocurrent density to 630 μA cm−2 relative to the reversible hydrogen electrode (RHE). These experimental results were validated by calculations using density functional theory (DFT), which revealed that HRG results in a significant charge redistribution and an improved photocatalytic hydrogen evolution reaction (HER).

  • Article

    Functionalized Carbon Honeycomb Membranes for Reverse Osmosis Water Desalination

    (Wiley, 2023-08-30) Voronin, Aleksandr S.; Ho, Duc Tam; Schwingenschlögl, Udo; Physical Science and Engineering Division King Abdullah University of Science and Technology Thuwal 23955-6900 Kingdom of Saudi Arabia; Physical Science and Engineering (PSE) Division; Material Science and Engineering Program; Applied Physics; KAUST Solar Center (KSC); Department of Mechanical and Construction Engineering Faculty of Engineering and Environment Northumbria University Newcastle upon Tyne NE1 8ST UK

    Reverse osmosis desalination is a common technique to obtain fresh water from saltwater. Conventional membranes suffer from a trade-off between salt rejection and water permeability, raising a need for developing new classes of membranes. C-based membranes with porous graphene and carbon nanotubes offer high salt rejection, water permeability, and fouling resistance. However, controlling the pore size of these membranes is challenging. Therefore, a carbon honeycomb membrane is studied using classical molecular dynamics simulations. It is reported that functionalization with −COO– groups provides 100% salt rejection with around 1000 times higher water permeability than conventional polyamide membranes. Atomic-level understanding of the effect of the functional groups' location on salt rejection and water permeability is developed.