Symmetry-Breaking Charge Separation in the Solid State Using Perylenemonoimide-Based Multichromophoric Architectures

Symmetry-breaking charge separation (SB-CS) results in the generation of electron–hole pairs via photoexcitation. SB-CS in chromophoric self-assemblies can potentially be an important route to enhancing the open-circuit voltage of organic photovoltaics. Although SB-CS properties of perylenediimide derivatives are investigated mostly in the solution state by changing the solvent dielectric constant, herein, we have investigated SB-CS in the thin films of two multichromophoric perylenemonoimide (PMI) derivatives, namely, Bz(PMI)3 and Bz(PMI)4, where PMI has been functionalized with a benzene ring via an acetylene linker. We have characterized these molecules with various analytical techniques, including steady-state absorption and emission spectroscopy. Furthermore, to understand the SB-CS dynamics, we performed a femtosecond and nanosecond transient absorption spectroscopic investigation and analysis. We observed SB-CS in solution aggregates and solid-state thin films, which were not observed in their monomers in solution. The observation of solid-state SB-CS is promising for the potential utilization of these molecules in organic photovoltaics.