Band-like transport in non-fullerene acceptor semiconductor Y6.

The recently reported non-fullerene acceptor (NFA) Y6 has been extensively investigated for high-performance organic solar cells. However, its charge transport property and physics have not been fully studied. In this work, we acquired a deeper understanding of the charge transport in Y6 by fabricating and characterizing thin-film transistors (TFTs), and found that the electron mobility of Y6 is over 0.3-0.4 cm/(V⋅s) in top-gate bottom-contact devices, which is at least one order of magnitude higher than that of another well-known NFA ITIC. More importantly, we observed band-like transport in Y6 spin-coated films through temperature-dependent measurements on TFTs. This is particularly amazing since such transport behavior is rarely seen in polycrystalline organic semiconductor films. Further morphology characterization and discussions indicate that the band-like transport originates from the unique molecule packing motif of Y6 and the special phase of the film. As such, this work not only demonstrates the superior charge transport property of Y6, but also suggests the great potential of developing high-mobility n-type organic semiconductors, on the basis of Y6.