Self-Assembled Monolayers of Cyclohexyl-Terminated Phosphonic Acids as a General Dielectric Surface for High-Performance Organic Thin-Film Transistors

摘要

Self-assembled monolayers (SAMs) provide a versatile molecular platform that can dramatically change the surface properties by varying the terminal groups. The cyclohexyl group is an unprecedented terminal group for all kinds of SAMs, to the best of our knowledge. Interestingly, cyclohexyl terminal groups are present in the phospholipid bilayers of acid- and heat-resistant bacteria (Bacillus acidocaldarius), and make a major contribution to the acid- and heat-tolerance of the cell membrane. Here, we report a novel cyclohexyl-terminated SAM from 12-cyclohexyldodecylphosphonic acid (CDPA in Figure 1a). The most important finding from this study is that molecules of CDPA self-assemble into a highly ordered molecular monolayer on AlO_y/TiO_x, a solution-processed high-k metal oxide, providing a general dielectric surface for high-performance organic thin-film transistors (OTFTs). The CDPA-modified AlO_y/TiO_x functions as an excellent dielectric enabling OTFTs with high field effect mobility of up to 5.7 cm~2 V~(-1) s~(-1) for holes and 5.5 cm~2 V~(-1) s~(-1) for electrons, good air stability with low operating voltage, and general applicability to solution-processed and vacuum-deposited p-type and n-type organic semiconductors.