Excitation Dynamics of a Low Bandgap Silicon-bridged Dithiophene Copolymer and its Composites with Fullerenes
Journal
Applied Physics Letters
Date Issued
April 9, 2012
Abstract
We report on excitation dynamics in pristine and bulk heterojunction films of the low bandgap silicon-bridged dithiophene copolymer poly[(4,4′-bis(2- ethylhexyl)dithieno[3,2-b:2′, 3′-d]silole)-2,6-diyl-alt-(4,7-bis(2- thienyl)-2,1,3-benzothiadiazole)-5,5′-diyl] with methanofullerene derivatives. The combination of ultrafast transient transmission and photoluminescence allows us to probe the relaxation of both exciton and polaron states in a relatively wide spectral and temporal range. Measurements reveal that the majority of excitations undergo ultrashort non-radiative relaxation while a small fraction of the photoexcited species decays slowly within hundreds of ps. In the blend films, significantly longer decays are observed suggesting the presence of long lived holes and/or charged-transfer type of excitons. © 2012 American Institute of Physics.