  Molecules which exhibit thermally activated delayed fluorescence (TADF) show
great promise for use in efficient, environmentally-friendly OLEDs, and thus
the design of new TADF emitters is an active area of research. However, when
used in devices, they are typically in the form of disordered thin films, where
both the external molecular environment and thermally-induced internal
variations in parameters such as the torsion angle can strongly influence their
electronic structure. In this work, we use density functional theory and X-ray
photoelectron spectroscopy to investigate the impact of disorder on both core
and valence states in the TADF emitter 2CzPN. By simulating gas phase molecules
displaying varying levels of disorder, we assess the relative sensitivity of
the different states to factors such as varying torsion angle. The theoretical
results for both core and valence states show good agreement with experiment,
thereby also highlighting the advantages of our approach for interpreting
experimental spectra of large aromatic molecules, which are too complex to
interpret based solely on experimental data.
