Modeling Organic Electronics

ADF has several unique features to model processes at the molecular level such as charge transport, exciton coupling, and phosphorescence. These molecular process are important for optimizing the performance of materials used in organic electronics devices such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), photovoltaics (PVs and OPVs), and dye-sensitized solar cells (DSSCs). See also the webinar with Symbeyond on Multiscale optimization of OLED materials and devices, a presentation on modeling organic electronics, a recent poster, an advanced tutorial on modeling OLED dyes, research publications, and an invited high-level article on modeling organic electronics with ADF.

OLED phosphorescence SOC-TDDFT

OLED phosphorescence with relativistic TDDFT

Organometallic complexes undergoing rapid intersystem crossing to a long-lived triplet state achieve high quantum efficiencies in OLED devices. Phosphorescence back to the ground state is spin-forbidden. To rationally design improved OLEDs, predict phosphorescent lifetimes and zero-field splittings with spin-orbit coupling TDDFT in ADF.

Optimize the emission color of OLED emitters by calculating the vibrationally resolved emission spectrum (see tutorial). Faster methods for these Franck-Condon factor calculations will be available in late 2019.

Intersystem crossing rates can be estimated from SOC matrix elements (SOCMEs) with ADF (see highlight).

Tutorial: calculating OLED phosphorescence
Optimizing TADF emission

TADF: minimize S-T gap, maximize SOCME

Organic or organometallic molecules which can quickly reverse intersystem cross from the T1 to the S1 state exhibit delayed fluorescence (TADF). To virtually screen improved TADF emitters, one could maximize SOC matrix elements (SOCMEs) with ADF, while simultaneously minimizing the S-T gap. With The averaged S-T SOCMEs are easy to grab from the standard output with the PRINT SOMATRIX.

Effective TADF emitters usually have spatially separated HOMO and LUMOs, which are more accurately described by using a tuned range-separated hybrid (RSH). A PLAMS script automates such tuning (see tutorial).

Tutorial: optimizing TADF emission
Vibrational progression Pt OLED emitter

Vibrational fine structure emitters and dyes

The color of an OLED emitter or solar cell dye depends on the main emission / absorption peak as well as on the vibrational progression. The peaks where there is also a change in vibrational quantum number affect the overal spectrum and can have a big effect on perceived color or incident photon conversion efficiency.
In ADF and AMS you can calculate the Franck-Condon factors and the vibrationally resolved spectra which will help to optimize your OLED emitter or solar cell dye.

Vibronic fine structure tutorial
Anisotropic hole mobility in organic semi-conductor

OFETs: transfer integrals for hole/electron mobility

Carrier mobility is crucial for OFETs and other organic electronic devices. For meso-scale modeling of hole and electron hopping, electronic transport properties between molecular fragments can be calculated at the DFT level with ADF in three different ways:

  • Charge transfer integrals (see tutorial, video)
  • Coupled frozen-density embedding (see webinar)
  • Non-equilibrium Green’s functions

The periodic DFT code BAND calculates effective masses, which can be used to calculate mobilities with the band transport model.

Tutorial: mobility with charge transfer integrals
spin-orbit coupling increases DSSC efficiency

DSSCs: excitation, e– injection, regeneration

Excitation spectra of Ru and Os dyes are accurately predicted with spin-orbit coupling TDDFT. The unique fragment-based approach in ADF has been used to scrutinize the available energy for electron injection into TiO2 after dye excitation.
Modern functionals, relativistic effects and solvation were employed to study N3 dye regeneration.
In BAND, electric fields and solvation effects (COSMO) on molecule-surface interactions can be modeled with proper 2D periodicity.

We have selected a number of relevant publications where ADF has been used to study organic electronics.

Try out ADF yourself!

Perovskites: electronic structure, dynamics

Relativistic TDDFT calculations help unravel the solution chemistry of lead halides. Similarly, NMR calculations can assist the determination of the microstructure in perovskite crystals.

Advanced bonding analysis (COOP) gives detailed insight in how the bonding interactions and relativistic effects in perovksites affect the band gaps.

Ongoing efforts include DFTB and ReaxFF studies to understand dynamical and larger-scale electronic and reactive (degradation) properties in perovskite materials.

Literature Highlights

All highlights