Impact of the core on the inter-branch exciton exchange in dendrimers

Abstract

Organic dendrimers with p conjugated systems are capable of capturing solar energy as a renewable source forhuman use. Nonetheless, further study regarding the relationship between the structure and the energy transfermechanism in these types of molecules is still necessary. In this work, nonadiabatic excited state moleculardynamics (NEXMD) were carried out to study the intra- and inter-branch exciton migration in two tetrabranched dendrimers, C(dSSB)4 and Ad(BuSSB)4, which differ in their respective carbon and adamantane core.Both systems undergo a ladder decay mechanism between excited states, with back-and-forth transitionsbetween S1 and S2. Despite presenting very similar absorption–emission spectra, differences in the photoinduced energy relaxation are observed. The size of the core impacts the inter-branch energy exchange andtransient exciton localization/delocalization, which ultimately condition the relative energy relaxation rates, beingfaster in Ad(BuSSB)4 with respect to C(dSSB)4. Nevertheless, the photoinduced processes lead to a progressivefinal exciton-self-trapping in one of the branches of both dendrimers, which is a desirable feature in organicphotovoltaic applications. Our results can inspire the design of more efficient dendrimers with the desiredmagnitude of inter-branch exciton exchange and localization/delocalization according to changes in their core.