1 research outputs found
Measuring Charge-Separation Dynamics via Oligomer Length Variation
We study the optically induced charge-transfer
dynamics in donor–acceptor oligomers of different chain lengths.
The combination of systematic synthesis, electrochemical measurements,
and ultrafast transient absorption spectroscopy allows us to determine
the charge-transfer properties and dynamics in donor–acceptor
systems of confined lengths. Calculations within Marcus and Jortner
electron-transfer theory explain the different charge-recombination
times. For compounds in which complete charge separation can occur
we deduce fast equilibration between different charge-transfer configurations
prior to charge recombination. Thus, monoexponential charge-recombination
kinetics are observed, as only the smallest-barrier configuration
leads to relaxation to the ground state. The systematic oligomer length
variation along with time-resolved spectroscopy allows us to determine
how far apart charges can be separated in multichromophore donor–acceptor
systems. Such information is relevant for understanding on a microscopic
level the charge carrier mobility in materials for organic electronics
and photovoltaics