Effects of energy offsets and molecular packing on exciton and charge carrier dynamics in small-molecule donor-acceptor composites

摘要

We present a study of optical, photoluminescent (PL), and photoconductive properties of small-molecule D/A bulk het-erojunctions of functionalized fluorinated anthradithiophene (ADT-R-F) and pentacene (Pn-R-F8) derivatives. We chose one of the ADT derivatives, ADT-TES-F, which exhibits a 2D "brick-work" π-stacking, as the donor, and ADT-TIPS-F (2D "brick-work"), ADT-TSBS-F (ID "sandwich-herringbone"), Pn-TIPS-F8 (2D "brick-work"), or Pn-TCHS-F8 (ID "sandwich-herringbone"), as acceptors. We measured PL and photoconductivity at time scales from sub-nanoseconds to many seconds after photoexcitation, at various acceptor concentrations, under various experimental conditions. The choice of acceptors enabled us to distinguish between effects of the LUMO energy offsets between the donor and acceptor molecules and those of the molecular packing in the acceptor domains on exciton and charge carrier dynamics.