Recent Developments on Understanding Charge Transfer in Molecular Electron Donor‐Acceptor Systems

Charge transfer (CT) in molecular electron donor‐acceptor systems is pivotal for artificial photosynthesis, photocatalysis, photovoltaics and fundamental photochemistry. We summarized the recent development in study of CT and discussed its application in thermally activated delayed fluorescence (TADF) emitters. The direct experimental proof of the spin multiplicity of the charge separated (CS) state with pulsed laser excited time‐resolved electron paramagnetic resonance (TREPR) spectroscopy was discussed. Experimental determination of the electron exchange energy (J) of the CS state, with magnetic field effect on its yield or lifetime was introduced. The electron spin transfer accompanying the CT, studied with pulsed EPR spectra was briefly discussed. Tuning of the CT yield and kinetics with selective vibration excitation of the linker (the bridge) with IR pulse was presented. Above all, these studies show that there are more fun than simply monitoring the formation of the cations and anions and the kinetics or CS yields in this area. We introduce a few interesting topics on charge transfer (CT) in organic donor‐acceptor systems, include the exciton confinement, symmetry breaking CT, detection of dark states in TADF emitters, discrimination of the singlet and triplet charge separated (CS) states, magnetic effect on charge transfer, determination of the electron exchange energy (J), electron spin transfer accompanying the CT process, and vibration modulated CT process.