Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Designing new electronic materials with tailore...

Designing new electronic materials with tailored transport properties

Seminar given at Queen Mary University of London, 2023

Alex Ganose

May 17, 2023
Tweet

More Decks by Alex Ganose

Other Decks in Research

Transcript

  1. Alex Ganose Imperial College London, UK Virtual Atoms Lab: https:/

    /virtualatoms.org Designing new electronic materials with tailored transport properties
  2. Thermoelectrics convert waste heat into electrical energy Thermoelectric figure of

    merit: 𝛼 = Seebeck coefficient 𝜎 = conductivity 𝑇 = temperature 𝑘!"## = lattice thermal conductivity 𝑘$!$% = electrical thermal conductivity Snyder and Toberer, Nat. Mater. 7, 105 (2008)
  3. Computational prediction of experimentally verified thermoelectrics is rare Urban; Menon;

    Tian; Jain; Hippalgaonkar, J. Appl. Phys. 125, 180902 (2019) 2008 2012 2016 2020 Year 0.0 0.4 0.8 1.2 1.6 Exp. ZT n-LiZnSb p-SnS p-NbFeSb p-TmAgTe2 p-YCuTe2 n-Er12 Co5 Bi n-KAlSb4 p-Cd1.6 Cu3.4 In3 Te8 p-TaFeSb n-type p-type
  4. τ ... constant lifetime A hierarchy of methods exist for

    calculating electron lifetimes Pros: – Quick – Widely used Cons: – Fixed lifetime – Arbitrary results
  5. τ ... ∝ DOS–1 constant lifetime A hierarchy of methods

    exist for calculating electron lifetimes Pros: – Quick – Models acoustic phonon scattering Cons: – Still arbitrary – Fixed scattering process
  6. τ ... DFPT ∝ DOS–1 constant lifetime A hierarchy of

    methods exist for calculating electron lifetimes Pros: – First principles matrix elements – High accuracy Cons: – Expensive – Limited to <~20 atoms
  7. τ ... DFPT AMSET ∝ DOS–1 constant lifetime Calculate scattering

    rates but remain computationally efficient close to accuracy of DFPT+Wannier at 1/500th computational cost AMSET is a new framework for calculating transport properties Ganose et al. Nat. Commun. 12, 2222 (2021)
  8. All inputs obtained through DFT calculations primary input: uniform band

    structure calculation Ganose et al. Nat. Commun. 12, 2222 (2021)
  9. Electronic structure Fourier interpolated onto dense mesh Fourier interpolation of

    eigenvalues of group velocities Ganose et al. Nat. Commun. 12, 2222 (2021)
  10. Band- and k-dependent scattering rates obtained on dense mesh lifetimes

    from first principles inputs — no fitting parameters used Ganose et al. Nat. Commun. 12, 2222 (2021)
  11. Transport properties obtained from Boltzmann transport eqn calculate mobility, conductivity,

    Seebeck & thermal conductivity Ganose et al. Nat. Commun. 12, 2222 (2021)
  12. Multiple scattering mechanisms incorporated through computationally cheap matrix elements acoustic

    deformation potential (AD) deformation potential, elastic constant ionized impurity (II) dielectric constant polar optical phonon (PO) dielectric constant, polar phonon frequency Ganose et al. Nat. Commun. 12, 2222 (2021)
  13. AMSET provides insights into transport physics First principles inputs No

    fitting or tuning parameters 10 min runtime on laptop Ganose et al. Nat. Commun. 12, 2222 (2021)
  14. AMSET shows close agreement to experiment for the mobility across

    many materials All calculations with PBE functional Comparisons against single crystal measurements Ganose et al. Nat. Commun. 12, 2222 (2021)
  15. AMSET is an open-source python package you can run today

    Docs: https://hackingmaterials.lbl.gov/amset/ Support: https://matsci.org/c/amset Installation pip install amset Usage amset run --static-dielectric 10 ... Can be controlled through the command line or python interface Ganose et al. Nat. Commun. 12, 2222 (2021)
  16. Carrier mobility is a key materials property that is relatively

    independent of carrier concentration how quickly an electron or hole moves when pulled by an electric field µ = σ/en mobility conductivity carrier concentration
  17. Temperature dependence of carrier mobility has been used since ~1930

    to understand the quantum behaviour of materials First expressions for mobility in semiconductors include a T –3/2 dependence
  18. 25 years later, these expressions do remarkably well predicted the

    transport in n-type Germanium Impressive, since Wilson’s was the first to treat: 1. Valence/conduction bands separated by a gap 2. Impurities as the source of free carriers 3. Lattice vibrations as the source of scattering
  19. Since then, the T-dependence of mobility has been used as

    experimental signature of the dominant scattering mechanism Acoustic/optical deformation µ~T –3/2 Polar optical µ~T –0.75 Alloy µ~T –1/2 Ionized impurity µ~T 3/2
  20. Since then, the T-dependence of mobility has been used as

    experimental signature of the dominant scattering mechanism Acoustic/optical deformation µ~T –3/2 Polar optical µ~T –0.75 Alloy µ~T –1/2 Ionized impurity µ~T 3/2 derived from simplified models in a single parabolic band yet limitations are often forgotten in thermoelectric studies
  21. As computational tools have improved/become tractable, theory tells a different

    picture modern approaches allow transport properties to be predicted quantitatively
  22. DFPT+Wannier shows excellent agreement across many materials / 1 341

    . ( (3 2 . 2  0 (  . 1 (  . 2 .1 7/ 0 ( .1 7/ . 1 ( .1 7/ . 1 ( .1 7/ Agrees with experiment across - scattering types - band structures - temperatures
  23. Tin selenide is the poster boy for thermoelectric materials, long

    assumed to be limited by acoustic phonons SnSe DFPT+Wannier obtains experimental mobility dependence of T –3/2 BUT polar optical phonons dominate scattering
  24. Does the T-dependence of mobility give insight into the dominant

    scattering mechanism Review of all DFPT+Wannier studies (60+ materials) No correlation between T- dependence and scattering type Ganose et al. submitted (2022) arXiv.2210.01746
  25. Does the T-dependence of mobility give insight into the dominant

    scattering mechanism Review of all DFPT+Wannier studies (60+ materials) No correlation between T- dependence and scattering type Not safe to assume scattering type based on T-dependence alone Ganose et al. submitted (2022) arXiv.2210.01746
  26. τ ... DFPT AMSET ∝ DOS–1 constant lifetime Calculate scattering

    rates but remain computationally efficient close to accuracy of DFPT+Wannier at 1/500th computational cost AMSET is a new framework for calculating transport properties Ganose et al. submitted (2022) arXiv.2210.01746
  27. Using AMSET calculations, we find the primary factor controlling T-dependence

    are the phonon frequencies Calculations on a single parabolic & isotropic band Phonon frequencies have large impact Ganose et al. submitted (2022) arXiv.2210.01746
  28. Using AMSET calculations, we find the primary factor controlling T-dependence

    are the phonon frequencies / 1 341 . ( (3 2 . 2  0 (  . 1 (  . 2 .1 7/ 0 ( .1 7/ . 1 ( .1 7/ . 1 ( .1 7/ Ganose et al. submitted (2022) arXiv.2210.01746
  29. / 1 341 . ( (3 2 . 2 

    0 (  . 1 (  . 2 .1 7/ 0 ( .1 7/ . 1 ( .1 7/ . 1 ( .1 7/ Using AMSET calculations, we find the primary factor controlling T-dependence are the phonon frequencies Phonon frequencies control T-dependence irrespective of scattering type Ganose et al. submitted (2022) arXiv.2210.01746
  30. Dielectric tensors ~8,000 Polar freqs ~8,000 Deform potentials ~3,000 Elastic

    tensors ~11,000 Band structures 24,000 Mobility database 24,000 We performed 24,000 mobility calculations using AMSET with machined learned materials parameters Ganose et al. submitted (2022) arXiv.2210.01746
  31. Average T-dependence for polar and acoustic phonon scattering are very

    similar across the full dataset Ganose et al. submitted (2022) arXiv.2210.01746
  32. Mobility dependence has been used to justify unphysical materials properties

    Material Fitted SnSe 24 eV PbTe 22 eV BiCuSeO 24 eV Calc 10 eV 7 eV 4 eV
  33. We have applied AMSET to many emerging energy materials Sb2

    Se3 Wang et al., ACS Energy Lett. 7, 2954–2960 (2022) BaBi2 O6 Spooner et al., Chem. Mater. 33, 7441–7456 (2022) ZnSb2 O6 Jackson et al., ACS Energy Lett. 7, 3807–3816 (2022)
  34. Discovering new p -type transparent conductors Transparent conductors are a

    vital technology n-type materials dominate: In2 O3 , SnO2 , ZnO p-type TCs needed for fully-transparent technologies
  35. Needs to be conductive Dopable (>1020 cm–3 carriers) High mobility

    (>50 cm2/Vs) Needs to be transparent Wide bandgap (>3.2 eV) What do we need in a p - type transparent electrode? valence band conduction band Eg > 3.2 eV
  36. The picture is more complicated – must consider matrix elements

    symmetry-forbidden transitions can widen the optical bandgap
  37. We performed a high-through search for p- type conductors with

    forbidden optical transitions 18,000 candidates Woods-Robinson et al. Matter, 2023 (accepted)
  38. Calculated optical absorption for all 18,000 materials – most materials

    have forbidden transitions ”forbidden energy difference”: Woods-Robinson et al. Matter, 2023 (accepted)
  39. Database of optical properties screened for plausible p- type candidates

    with large forbidden energy difference 579 candidates Woods-Robinson et al. Matter, 2023 (accepted)
  40. Hybrid DFT used to obtain a better bandgap and filter

    the candidates further 184 candidates Woods-Robinson et al. Matter, 2023 (accepted)
  41. Many materials would have been missed by conventional screening based

    on bandgap alone Would be excluded in conventional screening (184 candidates) Would be included in conventional screening Woods-Robinson et al. Matter, 2023 (accepted)
  42. Final stage is to evaluate dopability and mobility In2 O3

    & SnO2 emerge from n- type study validating the approach final candidates Woods-Robinson et al. Matter, 2023 (accepted)
  43. 6 promising p- type candidates were identified and validated through

    high-level calculations BeSiP2 has the potential to be doped n- or p- type Woods-Robinson et al. Matter, 2023 (accepted)
  44. What do we need in a p-type transparent electrode BAs

    is strongly p- type Woods-Robinson et al. Matter, 2023 (accepted)
  45. Both are highly conductive with high mobilities due to their

    small effective masses Even at degenerate doping mobility is ~100 cm2/Vs Woods-Robinson et al. Matter, 2023 (accepted)
  46. Conclusions Access to cheap and accurate mobility calculations through AMSET

    is proving insights into the electronic behaviour of materials challenged long-held assumptions on T-dependence of mobility enabling the screening of novel optoelectronics including TCs
  47. Acknowledgements Funding EPSRC DOE ECR Program Computing NERSC ARCHER2 MMMHub

    and you for your attention! Electron transport Anubhav Jain Junsoo Park Transparent conductors Rachel Woods-Robinson Yihuang Xiong Jimmy-Xuan Shen