modeling organic electronics with adf

Modeling Organic Electronics with ADF

1) OLEDs: phosphorescence2) Charge mobility (e.g. OFETs)3) PVs/DSSC: singlet fission, excitation, e- injection, regenerationpublished papers & unpublished calcs by Mr. Mori, Ryoka Inc.

http://www.scm.com/OrganicElectronics

Hartmut YersinHartmut YersinHartmut Yersin

Y. Suzuri et al., Sci. Technol. Adv. Mater. 15 (2014) 054202. doi:10.1088/1468-6996/15/5/054202

Organic Light-Emitting Diodes

Challenges:• Optimize triplet phosphorescence rate• Minimize triplet-triplet annihilation and triplet-polaron quenching• Optimize properties of host material (higher T energy)• Optimize mobility in electron / hole transport layers• Optimize out-coupling

Phosphorescent OLED emitters: SOC-TDDFT with solvation compares well with Expt.

K. Mori, T. P. M. Goumans, E. van Lenthe, F. Wang, Phys. Chem. Chem. Phys. 16, 14523 (2014)

Predicting phosphorescent rates of Ir(III) complexes Best correlation with pSOC, a pragmatic approach:TD-B3LYP/TZP/DZP//BP86/TZ2P/TZP

J. M. Younker and K. D. Dobbs, Correlating Experimental Photophysical Properties of Iridium(III) Complexes to Spin−Orbit Coupled TDDFT Predictions, J. Phys. Chem. C, 117, 25714-25723 (2013)

Vibronic fine structure OLED phosphor Pt complex: vibrational progression from T1 → S0 emission

Courtesy of Mr. Kento Mori, Ryoka, unpublished results

unpublished calcs by Mr. Mori, Ryoka Inc. on TSUBAME2.0, JACI

Methods to calculate charge mobilities • Hopping transport:

– Charge transfer integrals + other elements, directly printed– Electronic couplings from frozen-density embedding

• Band transport: effective mass tensors in BAND

• Non-equilibrium Green’s Function (NEGF)– transmission probabilities for single-molecule junctions– quick calculation: wide-band limit– also in BAND (periodic structures) and in DFTB (large systems) Q

Hole / electron mobilities• Ordered crystals (low T) => band-like transport

• Amorphous materials: incoherent hopping

• Accoustic deformation potential

mc: the effective mass along the direction of transportmd: the density of states mass, (ma mb)1/2

ac: the acoustic deformation potential, V dEvbm/dVB: the elastic modulusLeff: the length of the p-bonded core of the molecule

mmTkBLe

Effective transfer integral Jeff = electronic coupling V

• Definition of fragments • Matrix elements from ADF

C2HOMOks

C1HOMORP hJ

C2HOMO

C1HOMORP S

C1HOMOks

C1HOMORR hH

C2HOMOks

C2HOMOPP hH

extract dimer

Fragment C1

Fragment C2

Molecular crystal of pentacene

(a) “transfer integral”

(b) spatial overlap

(c) site energy

PPRRRPRP

SHHSJV

orthogonalization

Anisotropic hole mobilities in pentacene

S.-H. Wen et al., J. Phys. Chem. B 113, 8813 (2009)

Anisotropic mobility：

Oligofuran vs Oligothiophene

6F: 17 times larger than 6T

J.-D. Huang, S.-H. Wen, W.-Q. Deng, K.-L. Han, Simulation of Hole Mobility in α-Oligofuran Crystals. J. Phys. Chem. B 115, 2140-2147 (2011)

Hole transport in tetrathienoarenes

Y.-A. Duan et al., Organic Electronics 15, 602-613 (2014)

Transport in N-hetero-pentacenes

X.-K. Chen et al., Organic Electronics 13, 2832-2842 (2012)

Transport in ladder-type molecules

H.-L. Wei, Y.-F. Liu, Appl. Phys. A, in press(2014)

Environment effects: transport in 1D wires

A. A. Kocherzhenko et al., Effects of the Environment on Charge Transport in Molecular Wires, J. Phys. Chem. C. 116 25213-25225 (2012).

hybrid quantum-classical model with polarizable force field including dynamic and static disorder

Electronic couplings + environment with FDE:charge transfer, exciton, charge separation

Pavanello/Rutgers & Neugebauer/Muenster groups: Excitons: J. Chem. Phys. 138, 034104 (2013), long range charge separation: J. Chem. Phys. 140, 164103 (2014), charge transfer: J. Chem. Theory Comput. 2014, 10, 2546−2556

Linear scaling, environment response, constrain charge, excitation, spin, ...

Environment effects: frozen-density embedding

M. Pavanello, T. van Voorhis, L. Visscher, and J. Neugebauer, An accurate and linear-scaling method for calculating charge-transfer excitation energies and diabatic couplings, J. Chem. Phys. 138, 054101 (2013).

N C2H4 V 12 ΔE ex

2 … …

4 0.261 0.540

6 0.260 0.521

8 0.261 0.534

10 0.260 0.538

20 0.260 0.534

Scales linearly with number of molecules included in environmentEffect on couplings and excitation energy larger for more polar systems

Exciton couplings with frozen-density embedding

C. König et al., Direct determination of exciton couplings from subsystem time-dependent density-functional theory within the Tamm-Dancoff approximation, J. Chem. Phys. 138, 034104 (2013).

C. König and J. Neugebauer, Exciton Coupling Mechanisms Analyzed with Subsystem TDDFT: Direct vs. Pseudo Exchange Effects, J. Phys. Chem. B 117, 3480 (2013).

Band Transport

• Drude model [J. Phys. Chem. C 114, 10592 (2010)]

• Acoustic deformation potential model [Appl. Phys. Lett. 99, 062111 (2011)]

mc: the effective mass along the direction of transportmd: the density of states mass, (ma mb)1/2

ac: the acoustic deformation potential, V dEvbm/dVB: the elastic modulusLeff: the length of the p-bonded core of the molecule

mmTkBLe

: the mean relaxation time of the band statem: the effective mass of the charge carrier,

hopping transport (P, T1, T2) band transport (a, b) experiment

l (eV) V (eV) (cm2V-1s-1) m/m0 (cm2V-1s-1) (cm2V-1s-1)

Rubrene 0.1460 -0.082 7.22 0.99 36 20-40a

-0.015 0.29 2.44 14

-0.015 0.29

Pentacene 0.1008 -0.037 2.12 1.93 18 11-35b

0.084 6.06 10.90 3

0.055 3.14

DNTT 0.1272 -0.073 5.41 1.90 19 8.3c

0.089 5.05 2.83 12

0.012 0.11

C10-DNTT 0.1426 0.076 4.44 0.87 41 10d

-0.055 1.52 1.50 23

-0.055 1.52

C8-BTBT 0.2466 0.048 0.50 1.31 27 16.4e

0.022 0.07 1.66 21

0.022 0.07

Wide-band limit (NEGF): fast transmission calculations for single-molecule junctions

Thesis Christopher Verzijl, Thijssen group (Delft)

DFT-Based Molecular Transport Implementation in ADF/BAND. J. Phys. Chem. C, 116, 24393-24412 (2012).

NEGF in BAND

Nature Nanotechnology 8, 282–287 (2013) Calc.: Verzijl, Thijssen group (Delft)

BAND calculations explain break-through experiment on mechanical and electrostatic effects in molecular charge transport.

Image charges shift orbital levels => dominate through-molecule transport

NEGF in DFTB

Heine group (Jacobs U Bremen) Adv. Mater. 2013, 25, 5473–5475

Rippling in MoS2 strongly reduces conductance

Performance of these materials may strongly depend on production methods.

NEGF in DFTB

Heine group (Jacobs U Bremen) SCIENTIFIC REPORTS | 3 : 2961 (2013)

Conductance in SWNT vs MWNT

Singlet Fission Yields in Organic Crystals:

N. Renaud, P. A. Sherratt, and M. A. Ratner, Mapping the Relation between Stacking Geometries and Singlet Fission Yield in a Class of Organic Crystals, J. Phys. Chem. Lett., 4, 1065-1069 (2013)

Direct pathway dominates SF,depends on crystal packing

Mechanism of DSSCs N3: Most typical dye

Three steps – all treated with ADF：1. Photoexcitation of dye

2. Electron injection from dye to TiO2

3. Dye regeneration

Spin-orbit coupling increases dye efficiency

SOC-TDDFT: Incident photon to current efficiency (IPCE) of Ru sensitizer DX1 increased due to spectral broadening because of SOC

S. Fantacci, E. Ronca, and F. de Angelis, Impact of Spin–Orbit Coupling on Photocurrent Generation in Ruthenium Dye-Sensitized Solar Cells, J. Phys. Chem. Lett., 5, 375-380 (2014)

Spin-orbit coupling increases dye efficiency

SOC indispensible to describe low-energy absorption bands of Os dyes

E. Ronca, F. de Angelis, and S. Fantacci, TDDFT Modeling of Spin-Orbit Coupling in Ru and Os Solar Cell Sensitizers, J. Phys. Chem. C, just accepted

[Os(dcbpy)2(SCN)2]4-

expSR-TDDFT

SOC-TDDFT

Molecular design of Ru-dyes• Ligands with extended p systems

⇒ red shift + increased absorption

F. Gajardo et al., Inorg. Chem. 50, 5910 (2011)

Electron injection from Ru dye to TiO2

• Ruthenium polypiridyl dyes with extended π system shows an enhancement of its light harvesting capacity.

• However, it is not necessarily reflected by an increase of its efficiency as dye because an efficient electron injection from the dye to TiO2 does not always occur.

Absorbed energy Delivered energy

[Energy flow on a typical dye sensitized solar cell]

Energy adsorbed ≠ Energy to TiO2

Singlet

Triplet

Rational design of DSSC dyes

J. Phys. Chem. A 117, 430−438 (2013)

HOMO vs Hamett LUMO vs Hamett

Rational design of dyes for p-type DSSCLight-harvesting efficiency = 1 - 10-f

Charge-separation efficiency => increase hole-e- separation

Hole-injection efficiency, Koopman’s approximation:DERP = EHOMO(dye) - E(VB)(electrode)

J. Wang et al. J. Phys. Chem. C 117, 2245−2251 (2013)

Rational design of dyes for p-type DSSC

J. Phys. Chem. C 117, 2245−2251 (2013)

Large separation e- - electrode

Alkyne-spaced-ligands (4,6) also have high f => high Light Harvesting EfficiencyHole-injection efficiency large for all ligands

J. Am. Chem. Soc., 136, 2876−2884 (2014)

Charge generation in fullerene-based OPVs Charge generation facilitated by resonant coupling of singlet excitons in polymer donors to fullerene electronic states

Diagonal couplings

Off-diagonal couplings (transfer integrals)

Scientific Reports, 4: 4033 (2014)

New, Robust Organic Dye: 10% conversion

TiO2 / dye / I-/I3- redox couple

• spatially separated HOMO/LUMO: facilitate e- injection & dye regeneration • good alignment with TiO2 bands

Electron injection: Newns-Anderson

• Lorentzian distribution

• Center of the LUMO (ads) distribution

• Width of the broadening

ii Ep )ads(LUMO

iipE )ads(LUMO

2)ads(

ii Ep )ads(LUMO

)meV(/658)fs(

Electron injections time is obtained from lifetime broadening through:

Fitting of Lorentzian distribution to adsorbate LUMO PDOS ),( ii p

[J. Phys. Chem. B 2006, 110, 20513]

BINA on TiO2: injection times (Newns-Anderson)• 2D system • PDOS analysis

BINA’s LUMO

The calculated electron injection time based on the Newns-Anderson approach is 4.8 fs, below the exp. upper bound 7 fs [J. Phys. Chem. B 2004, 108, 3114].

Adsorbate PDOS

Total DOS

• Spin-Orbit Coupling, dispersion• COSMO solvation crucial• Formation N3-I2

- slowest step

N3 dye regeneration is rate-limiting step in DSSCs

A. M. Asaduzzaman and G. Schreckenbach, Interactions of the N3 dye with the iodide redox shuttle: quantum chemical mechanistic studies of the dye regeneration in the dye-sensitized solar cell. Physical Chemistry Chemical Physics, 13, 15148 (2011)

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