Broadband absorption and light-energy transfer in a phenyl-core thiophene dendrimer with multiple π-conjugations

Abstract

π-Conjugated dendrimers, with unique optical properties, have the potential to be used as light-harvesting antenna in organic solar cells and photodetectors. Here, the broadband absorption and light-energy transfer in a phenyl-core thiophene dendrimer, Ph-(7T)₃, have been investigated using quantum calculations and absorption, photoluminescence, and excitation spectroscopy. The broadband absorption of the highly branched Ph-(7T)₃ macromolecule could be attributed to multiple π-conjugations in Ph-(7T)₃ (due to phenylthiophene and thiophene oligomers with different numbers of thiophene units). The divergency of the wavelengths between photoluminescence and excitation light indicated that the multiple π-conjugating system exhibited various modes of excited-state relaxation, which could explain the light-energy transfer from the core to the thiophene dendrons. The fluorescent quantum yield and lifetime of this molecular system are also presented.