Tuning the donors to control the lifetimes of charge-separated states in triazine-based donor-acceptor systems

Six donor-acceptor systems with styrene based 9-phenyl carbazole, 4,4'-di(hydro, methyl, methoxy or octyloxy) triphenylamine and 4-methylphenyl indoline derivatives as donors, and s-triazine group as the acceptor were synthesized and characterized. The charge-separated states of these donor-acceptor systems were generated through the effective photoinduced electron transfers from excited donor modules to acceptor modules and had lifetimes ranging from 57 ns to 215 ns. These donor-acceptor systems are capable of fast charge separation, but have extremely slow charge recombination. The back electron transfer processes of these donor-acceptor systems occur in the inverted region of the Marcus curve, The driving forces of back electron transfer and the reorganization energies of electron transfer decrease in the order of 9-phenyl carbazole derivative, 4,4'-di(hydro, methyl, methoxy or octyloxy) triphenylamine derivative and 4-methylphenyl indoline derivative. These two factors work together to determine the different lifetimes of charge-separated states in these donor-acceptor systems. (C) 2016 Elsevier Ltd. All rights reserved.