Intersystem crossing processes in TADF emitters

Abstract

This book chapter gives a brief overview over quantum chemical methods for computing rate constants of radiative and nonradiative molecular excited-state processes and summarizes recent theoretical research on the photophysics of metalfree as well as copper-containing thermally activated delayed fluorescence (TADF) emitters. The methods for computing temperature-dependent intersystem crossing (ISC) and reverse intersystem crossing (rISC) rate constants focus on Fermi golden rule expressions whereas fluorescence and phosphorescence rate constants are determined employing multi-reference spin-orbit configuration interaction approaches. TADF and phosphorescence are competitive in many copper(I) complexes whereas TADF dominates in metal-free donor-acceptor systems. In addition to a small singlet-triplet energy splitting, spin-vibronic interactions are found to play an essential role in the ISC and rISC processes of metal-free TADF emitters.