Direct observation of ultrafast long-range charge separation at polymer-fullerene heterojunctions.

In polymeric semiconductors, charge carriers are polarons, which means that the excess charge deforms the molecular structure of the polymer chain that hosts it. This results in distinctive signatures in the vibrational modes of the polymer. Here, we probe polaron photogeneration dynamics at polymer:fullerene heterojunctions by monitoring its time-resolved resonance-Raman spectrum following ultrafast photoexcitation.

Large electronic bandwidth in solution-processable pyrene crystals: the role of close-packed crystal structure.

We examine the interdependence of structural and electronic properties of two substituted pyrene crystals by means of combined spectroscopic probes and density-functional theory calculations. Substituted pyrenes are useful model systems to unravel the interplay of crystal structure and electronic properties in organic semiconductors. To study the effect of steric encumbrance on the crystalline arrangement of two 1,3,6,8-tetraalkynylpyrene derivatives, one features linear n-hexyl side groups while the other contains branched trimethylsilyl groups.