Charge-transfer excitons in strongly coupled organic semiconductors

Time-resolved and temperature-dependent photoluminescence measurements on one-dimensional sexithiophene lattices reveal intrinsic branching of photoexcitations to two distinct species: self-trapped excitons and dark charge-transfer excitons (CTX; $\agt 5$\% yield), with radii spanning 2--3 sites. The significant CTX yield results from the strong charge-transfer character of the Frenkel exciton band due to the large free exciton bandwidth ($\sim400$\,meV) in these supramolecular nanostructures.