Layered Poly(3-hexylthiophene) Nanowhiskers Studiedby Atomic Force Microscopy and Kelvin Probe Force Microscopy.

The optoelectronic properties oforganic electronic materials aresignificantly affected by their molecular packing and local environments.Herein, atomic force microscopy (AFM) is used to characterize nanowhiskersof poly(3-hexylthiphene) (P3HT). The P3HT nanowhiskers form layeredstructures with distinctive heights that increase over time, suggestingthat layered structures are more thermodynamically favored in solution.Further inspection reveals that the monolayer (ML) nanowhiskers areconsistently wider than double-layered (DL) ones. The width disparityis likely due to the sliding of π–π stacked motifswithin ML nanowhiskers evident by the rougher edges of ML nanowhiskers.Conversely, the interfacial interactions between two P3HT monolayersmay inhibit the sliding of conjugated motifs inside the DL nanowhiskers,leading to much narrower and tightly packed structures. Kelvin probeforce microscopy (KPFM) measurements are carried out to investigatethe influence of ML and DL nanowhiskers’ morphologies and localenvironments on their electronic properties. Curved, vertically stacked,and overlapped regions show higher contact potential differences (CPD)resulting from a combined effect of irregular molecular packing andlocal environmental impacts. [ABSTRACT FROM AUTHOR]