Photophysical and Electrochemical Characterization of BODIPY-Containing Dyads Comparing the Influence of an A–D–A versus D–A Motif on Excited-State Photophysics

A complete photophysical characterization of organic molecules designed for use as molecular materials is critical in the design and construction of devices such as organic photovoltaics (OPV). The nature of a molecule’s excited state will be altered in molecules employing the same chromophoric units but possessing different molecular architectures. For this reason, we examine the photophysical reactions of two BODIPY-based D–A and A–D–A molecules, where D is the donor and A is the acceptor. A BODIPY (4,4′-difluoro-4-bora-3a,4a-diaza-s-indacene) moiety serves as the A component and is connected through the meso position using a 3-hexylthiophene linker to a N-(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]pyrrole (DTP), which serves as the D component. An A–D–A motif is compared to its corresponding D–A dyad counterpart. We show a potential advantage to the A–D–A motif over the D–A motif in creating longer-lived excited states. Transient absorption (TA) spectroscopy is used to characterize the photophysical evolutio...