The Flexible Linker Strikes Again - in a new paper from LIMNO

The solid-state self-assembly of molecular semiconductors is a key aspect for controlling the optoelectronic properties of organic electronic materials. In this work, we investigated the use of a flexible linker strategy to control the self-assembly of a solution-processable diketopyrrolopyrrole semiconductor coded as DPP(TBFu)₂. Two distinct dimers—prepared with varied linker position relative to the orientation of the conjugated core—reveal the effect of connectivity on the solid-state self-assembly and optoelectronic properties—favoring either H- or J-type aggregation. The dimer with a “vertical” linker orientation exhibits a poor crystallinity in neat films, but improves hole mobility in OFETs 10-fold, reaching 3.0 × 10^–3 cm²V^–1s^–1 when used as an additive in with DPP(TBFu)₂. Distinctively, the dimer with a “horizontal” linking orientation does not enhance charge carrier transport, but is found to affect the thermal stability of donor:acceptor blends in OPVs with PCBM. Devices retain 90% of their initial conversion efficiency after 5 hours of thermal stress, compared to only 45% for control devices. Thermodynamic and kinetic rationale further suggest that this flexible linker strategy represents a powerful tool to control supramolecular assembly in molecular semiconductors without altering the nature of the core conjugated segment.