Low-voltage, High-performance N-channel Organic Thin-film Transistors Based On Tantalum Pentoxide Insulator Modified By Polar Polymers

摘要

Polar polymers (polyfluorene copolymers, PFN-PBT) with different polarities are utilized to modify the surface of tantalum pentoxide (Ta_2O_5) insulator in n-channel organic thin-film transistors (OTFTs). A high mobility of 0.55 cm~2/Vs, high on/off current ratio of 1.7 × 10~5, and low threshold voltage of 2.8 V are attained for the OTFT with the modification polymers, the performances of which are much better than those of OTFT with only Ta_2O_5 insulator. The performances of the OTFT with only Ta_2O_5 insulator are only 0.006 cm~2/Vs in mobility, 5 × 10~3 in on/off ratio, and 12.5 V in threshold voltage. Furthermore, it is found that the threshold voltage of the OTFTs with PFN-PBT modification layer is easily tuned by polarities of the polymers. Further studies show that self-assembly dipole moments in the polymers play an important role in the improvement of the OTFT performances.