Simulation of Charge Transport in Oxides Simulation of Charge Transport in Oxides and Organic Semiconducting Materials and Organic Semiconducting Materials Jochen Blumberger University College London Trieste, 23.05.2014 kshop on Materials Challenges in Devices for Fuel Solar Production and Employ
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Simulation of Charge T ransport in Oxides and Organic Semiconducting Materials
Jochen Blumberger University College London Trieste, 23.05.2014. Simulation of Charge T ransport in Oxides and Organic Semiconducting Materials. Workshop on Materials Challenges in Devices for Fuel Solar Production and Employment. II. CT in oxide materials. Overview. - PowerPoint PPT Presentation
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Simulation of Charge Transport in Oxides and Organic Simulation of Charge Transport in Oxides and Organic Semiconducting MaterialsSemiconducting Materials
Jochen Blumberger
University College London
Trieste, 23.05.2014
Workshop on Materials Challenges in Devices for Fuel Solar Production and Employment
OverviewI. Theoretical background II. CT in oxide materials
III. CT in organic solar cell materials
IV. CT in bacterial nanowiresElectrode
e-
Food
Food
Microbe
Photoelectrochemical cell
e-
oxide good charge transport
essential for high efficiency
e-
Clarke and Durrant, Chem Rev. (2010)
Organic photovoltaic cell
good charge transport essential for high efficiency
Ishii, S. et al. Appl. Environ. Microbiol. 71, 7838 (2006).
Electrode
Food
e-Microbe
Mediatorless microbial fuel cell
Summers, Z. M. et al. Science 330, 1413 (2010).
good charge transport essential for high efficiency
Why computation ?
Nature of charge carrier (localised/delocalised)
Mechanism of charge transport (band/hopping/wavepacket)
Atomistic interpretation of measured charge mobilities, I-V curves
NanoStructure-property relationships
Overview
• I. Theoretical Background
• II. Electron tunneling between O-vacancies in MgO
• III. Electron transport in fullerenes
• IV. Electron transport in bacterial nanowires
Which theory is adequate?
Cha
rge
mob
ilit
y
electron-phonon couplingor reorganisation energy or trapping energy
Which theory is adequate?
Cha
rge
mob
ilit
y
electron-phonon couplingor reorganisation energy or trapping energy
metals
band theory
redox in solutionredox proteins
Small polaron hoppingET theories (Marcus)
Which theory is adequate?
Cha
rge
mob
ilit
y
electron-phonon couplingor reorganisation energy or trapping energy
metals
band theory
redox in solution redox proteins
Small polaron hoppingET theories (Marcus)
?
holes/e- in oxidesholes/e- in organicsemiconductors
Electron transfer theory (Thermally activated polaron hopping)
initial diabatic state final diabatic state
e-e-
Diabatic and adiabatic electronic states
Q reaction coordinate
λ reorganization energy
Hab electronic coupling matrix element
initial diabatic state
final diabatic statee-e-
adiabatic ground & 1st excited ET state
Diabatic and adiabatic electronic states
e-e-
Transition state theory
Nuclear tunneling
Landau-Zener theory
Diabatic states from constrained DFT (CDFT)
Idea: - Construct Hamiltonian in diabatic = charge localized basis
-Create charge localized states by adding an external
potential to Hamiltonian
=
Martin Karplus (1963) (?), Arieh Warshel (1993), Troy Van Voorhis (2005), John Tully
(2008),…
Charge constrained DFT (CDFT)
1. Define donor, acceptor and external potential w(r)
Q. Wu and T. van Voorhis, Phys. Rev. A 72, 024502 (2005)
Charge constrained DFT (CDFT)
1. Define donor, acceptor and external potential w(r)
2. Add Vw(r) to KS-equation
and vary V so that charge constraint
is fulfilled.
Q. Wu and T. van Voorhis, Phys. Rev. A 72, 024502 (2005)
Charge constrained DFT (CDFT)
1. Define donor, acceptor and external potential w(r)
2. Add Vw(r) to KS-equation
and vary V so that charge constraint
is fulfilled.
Q. Wu and T. van Voorhis, Phys. Rev. A 72, 024502 (2005)
diabatic state B ψB, EB = FB-VBN
1 AD qq
e-
e-
1 AD qq
diabatic state AψA, EA = FA-VAN
Charge constrained DFT (CDFT)
1. Define donor, acceptor and external potential w(r)
Q Wu and T Van Voorhis, Phys. Rev. A 72, 024502 (2005)
diabatic state B ψB, EB = FB-VBN
1 AD qq
e-
e-
1 AD qq
diabatic state AψA, EA = FA-VAN
CDFT Implementation in the CPMD code
• CDFT weight function for charge constraint:
where ρi are promolecular atomic densities (pseudo AO, Slater, Gaussians)
• CDFT wavefunction optimisation, geometry optimisation and BOMD
• GGA, hybrid and range separated hybrid functionals (with new HFX parallelisation)
• Troullier-Martins or Goedecker-Hutter pseudo potentials for core electrons
• Available in CPMD Version 3.15.1 (thanks to M. Boero and T. Laino)
H. Oberhofer, JB, J. Chem. Phys. 131, 064101 (2009)H. Oberhofer, JB, J. Chem. Phys. 133, 244105 (2010)