The target of the master thesis is to reproduce the experimental results of
the singlet-triplet gap tuning of triphenylene based polymers. After
introducing the theoretical basics of time dependent density functional
theory (TDDFT) and different exchange correlation (XC) functionals, the
specific methods and challenges are discussed. By means of standard and
long-range corrected (LRC) TDDFT methods, the absorption and emission
energies and the triplet localization behavior is calculated then for different
types of polymers and one monomer. The experimentally observed fixed
phosphorescence energy is not reproduced because the localization pattern
is different to the expectations: Instead of localizing on the triphenylene
unit - which is the backbone unit of all types of polymers - the triplet state
localizes in the TDDFT calculations on the different bridging units. This
leads to different triplet emission energies for each type of polymer.
However, the phosphorescence energy of the pure triphenylene chain is
predicted accurately by means of the LRC-PBE XC functional and slightly
less accurate by the standard hybrid B3LYP. Yet, the possible reasons for
the deviating results for the other polymers indicate that LRC TDDFT has
the potential to predict the triplet emission energies as well as the
localization behavior more accurate than with standard XC functionals.