Crossover from Single-Step Tunneling to Multistep Hopping for Molecular Triplet Energy Transfer

Abstract

Tracking Triplet-State Transfers In devices such as organic transistors and photovoltaic cells, energy flow from donor to acceptor sites can occur via electrons that have been excited into higher electronic levels, which create a triplet state with two unpaired spins. At short distances between donor and acceptor, the transfer occurs through direct tunneling, but at longer distances, the electron “hops” in a multistep process. Vura-Weis et al. (p. 1547 ) used femtosecond transient absorption spectroscopy to observe this crossover in transfer mechanism directly in a series of molecules with varying bridge lengths between the donor and acceptor.