posted on 2024-01-30, 15:05authored byRachael Richards, Yuqi Song, Luke O’Connor, Xiao Wang, Eric A. Dailing, Arthur E. Bragg, Alexander L. Ayzner
Artificial light
harvesting, a process that involves
converting
sunlight into chemical potential energy, is considered to be a promising
part of the overall solution to address urgent global energy challenges.
Conjugated polyelectrolyte complexes (CPECs) are particularly attractive
for this purpose due to their extended electronic states, tunable
assembly thermodynamics, and sensitivity to their local environment.
Importantly, ionically assembled complexes of conjugated polyelectrolytes
can act as efficient donor–acceptor pairs for electronic energy
transfer (EET). However, to be of use in material applications, we
must understand how modifying the chemical structure of the CPE backbone
alters the EET rate beyond spectral overlap considerations. In this
report we investigate the dependence of the EET efficiency and rate
on the electronic structure and excitonic wave function of the CPE
backbone. To do so, we synthesized a series of alternating copolymers
where the electronic states are systematically altered by introducing
comonomers with electron withdrawing and electron-rich character while
keeping the linear ionic charge density nearly fixed. We find evidence
that the excitonic coupling may be significantly affected by the exciton
delocalization radius, in accordance with analytical models based
on the line-dipole approximation and quantum chemistry calculations.
Our results imply that care should be taken when selecting CPE components
for optimal CPEC EET. These results have implications for using CPECs
as key components in water-based light-harvesting materials, either
as standalone assemblies or as adsorbates on nanoparticles and thin
films.