Synthesis and Characterization of Contorted Pentabenzo-Fused Coronenes as Semiconducting Materials.

Here, we report the synthesis and characterization of a series of contorted, yet noncentrosymmetrical, polycyclic aromatic hydrocarbons with a pentabenzo-fused coronene as the core framework. The parent pentabenzo[a,d,g,j,m]coronene (PBC) compound is shown to exhibit a shifted and rotated type of π-π stacking interactions, which render this series a semiconducting material. Single-crystal-based field-effect transistor devices of PBC exhibited efficient charge transport behavior, giving a p-channel field-effect mobility of 0.42 cm2 V-1 s-1 and an on/off ratio of 105.

Effect of interfacial structure on the transistor properties: probing the role of surface modification of gate dielectrics with self-assembled monolayer using organic single-crystal field-effect transistors.

Single-crystal field-effect transistors based on 2,3-dimethylpentacene have been used to probe the effect of surface modification of the insulating dielectric SiO(2) layer on the transistor characteristics. Self-assembled monolayers (SAMs) of different chain lengths and functional groups were used to systematically modify the structure and property of the semiconductor/dielectric interface. The charge carrier mobility as a function of SAM used for surface modification was analyzed. The character of the terminal functional group, as well as the mechanic treatment (rubbing) of the monolayer, much influences the carrier mobility. Introduction of a polar end group (donor or acceptor type) decreases the mobility compared to a nonpolar end group. Prerubbing of the monolayer serves to increase the charge carrier mobility by a factor of 2-4-fold. The results are interpreted in terms of the orderliness of the monolayer which affects the contact at the monolayer/semiconductor interface, which in turn affects the trapping sites' density or the smoothness of the potential surface that the carriers experience while transporting along the interface.