Adv. Mater. http://dx.doi.org/10.1002/adma.201302838 (2013)

Very fast charge transport can be achieved in small semiconducting molecules arranged in single crystals, because the absence of positional and energetic disorder in these structures reduces the number of trap states detrimental for conduction. For this reason, researchers are developing large-scale-oriented approaches based on direct deposition from solution that can produce conducting layers with high structural order. Peter Diemer and collaborators now show that mechanical vibrations can be the key to boost the performance of solution-deposited thin films. They use two audio speakers transmitting low-frequency sounds to gently shake small molecules drop-casted on a dielectric substrate; this additional mechanical energy provided during crystallization allows the molecules to reach a stable packing configuration that minimizes positional displacements. Transistors based on the obtained conducting layers show improved mobility, as well as reduced threshold voltage and hysteresis. The researchers suggest that this room-temperature strategy can prove particularly useful for organic materials that are sensitive to thermal-induced degradation.