Modeling molecular properties for organic electronics
OLED emitters, charge mobilities, and other properties
K. Mori,a T.P.M. Goumans,b* E. van Lenthe,b F. Wangca) Ryoka Systems Inc., Tokyo Skytree East Tower 1-1-2, Oshiage, Sumida-ku, Tokyo 131-0045, Japanb) Software for Chemistry & Materials, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlandsc) College of Chemistry, Sichuan University, 24, South Section 1, Yihuan Road, Chengdu, P. R. China* goumans@scm.com

Phosphorescent emitters

Virtual screening OLED emitters

Organic light-emitting diodes (OLEDs) convert electricity
into light, by emitting from excited states (excitons) formed
upon recombination of charges. Phosphorescent OLEDs
improve the conversion efficiency by harvesting all
excitons as triplets which subsequently phosphoresce.

Novel OLED emitters can be screened and optimized
through modern computational chemistry techniques.
Spin-orbit coupling TDDFT in ADF reliably predicts
phosphorescent lifetimes and zero-field splitting (ZFS)
across a diverse range or transition metal complexes.

Y. Suzuri et al., Sci. Technol. Adv. Mater. 15 (2014) 054202.
OLED efficiency can be optimized by maximizing intersystemcrossing and phosphorescence rates. This in turn iseffectuated by transition metal complexes with large spinorbit coupling, which mixes singlet and triplet states.

K. Mori et al., Phys. Chem. Phys. Chem.16, 14523 (2014)
See also Younker and Dobbs, J. Phys. Chem. C, 117, 2571425723 (2013) for a pragmatic screening approach.

Rational design of organic electronics with modern computational chemistry,giving a handle on several important material properties at the molecular level.
Charge carrier mobility

Exciton coupling & quenching

Hole and electron mobilities are also important properties
for optimizing organic electronic devices (OLEDs, OFETs,OPVs). The charge transfer integral approach in ADF is anefficient way to screen hopping rates, from which charge
mobilities magnitudes and anisotropy can be calculated.

Besides charge generation and mobility, the FDE approachin principle gives access to other properties of interest fororganic electronics: exciton coupling, singlet fission,
exciton-polaron coupling, exciton-exciton quenching, etc.

König et al., J. Chem. Phys. 138, 034104 (2013)

S.-H. Wen et al., J. Phys. Chem. B 113, 8813-8819 (2009)
A more sophisticated, all electron method to calculate
electronic couplings is available via the frozen-density
embedding (FDE) formalism from the Neugebauer &Pavanello groups. Environment effects (polarization) can beincludes and charges and excitons can be localized.
In the same ansatz, charge carrier generation from excitons
can be modeled (J. Chem. Phys. 140, 164103 (2014).

Intersystem crossing, TADF
Triplet to singlet intersystem crossing in organometallic
dopants is also dominated by spin-orbit coupling and canthus be assessed with ADF, e.g. Phys. Chem. Chem. Phys.
16, 26184-26192 (2014).
To optimize reverse intersystem crossing, important forthermally activated delayed fluorescence (TADF), theanalysis tools in ADF can be used to scrutinize the chargetransfer excitations and minimize the S-T gap.

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