Energy Transfer Dynamics in Complexes of Oppositely Charged Conjugated Polyelectrolytes

Conjugated polyelectrolytes (CPEs) are an attractive class of materials for light harvesting in energy applications due to their high absorption cross section, spectral tunability, delocalized electronic states, and tendency toward ionic self-assembly in water. These features make them well suited to mimicking natural electronic energy transfer (EET) relays – using donor-acceptor complexes of oppositely charged CPEs in place of biological pigments. However, the electronic properties of CPEs are highly complex, having a significant interplay between polyelectrolyte backbone microstructure, intra- and inter- chain aggregation, and local chemical environment. Understanding EET in such complexes represents a serious challenge, as the CPE microstructure – and hence electronic properties – are highly perturbed upon complexation. I will discuss recent work characterizing EET dynamics in a series of stable oppositely charged CPE complexes using time-resolved fluorescence anisotropy, transient absorption, as well as steady-state measurements to probe the relationship between CPE complex structure and EET. We find that both the excited-state dynamics and the complex morphology are very sensitive to relative energy donor/acceptor polyion charge ratio, allowing us to control the EET process.