Charge-carrier relaxation dynamics of poly(3-hexylthiophene)-coated gold hybrid nanoparticles

Poly(3-hexylthiophene)-coated gold (Au@P3HT) hybrid nanoparticles have been prepared via a “grafting-to” approach, and compared with pristine P3HT to investigate the dynamics of exciton relaxation using time-resolved transient-absorption and fluorescence spectroscopy. In efforts to facilitate the efficient dissociation of photo-generated excitons, we have incorporated gold nanoparticles having surface-plasmon resonances into thiol-terminated P3HT to fabricate Au@P3HT nanocomposites. The first-excited singlet state of Au@P3HT decays faster than that of pristine P3HT due to interactions with surface-plasmon resonances; excitons undergo dissociation via energy transfer from P3HT to the surface-plasmon state of a gold nanoparticle in Au@P3HT nanocomposites. The lowest triplet state of P3HT is also less populated due to the energy transfer while its lifetime is slightly reduced by the presence of gold nanoparticles. Thus, it is suggested that our incorporation of gold nanoparticles into P3HT reduces the recombination of geminate excitons and, thereby, increases the probability of exciton dissociation.