Modulation Of Microstructure And Charge Transport In Polymer Monolayer Transistors By Solution Aging

Main observation and conclusion A few monolayers of organic semiconductors adjacent to the dielectric layer are of vital importance in organic field-effect transistors due to their dominant role in charge transport. In this report, the 2-nm-thick polymer monolayers based on poly(3-hexylthiophene) with different molecular weights (M-n) were fabricated using dip-coating technique. During the monolayer (solid state) formation from the solution, a disorder-to-order transition of polymer conformation is observed through UV-vis absorption measurement. Meanwhile, high M-n polymer monolayer generates higher crystalline fibrillar microstructure than the low M-n one due to the stronger pi-pi intermolecular packing between polymers. More importantly, the solution aging procedure is utilized to further improve the morphology of polymer monolayers. It is obvious that after aging for 6 d, both fiber dimension and density as well as conjugation length are significantly increased under the same processing conditions in comparison to the fresh solution, and consequently the field-effect mobilities are remarkably enhanced by 2-4 times. Note that the maximum mobility of 0.027 cm(2)center dot V-1 center dot s(-1) is among the highest reported values for poly(3-hexylthiophene) monolayer transistors. These results demonstrate a simple but powerful strategy for boosting the device performance of polymer monolayer transistors.