Pendant Group Effect of Polymeric Dielectrics on the Performance of Organic Thin Film Transistors

Polymer dielectric is superior to its inorganic counterparts due to not only the low cost and intrinsic flexibility, but also the readily tunable dielectric constant, surface charge trap density, charge ejection and releasing ability and dipole moment, and all these properties play decisive roles in regulating the characteristic and performances of organic thin film transistors(OTFT). However, systematical studies on the relationship between structure and properties of polymeric dielectrics are rare. To this end, a series of polymeric dielectrics with well-defined linkages(ester or amide bonds) and predesigned pendant groups(alkyl-and aromatic-groups) are synthesized in high yields. Detailed studies show that the polyamide dielectrics exhibit higher dielectric constant,surface charge trapping density, and better charge storage capability than corresponding polyester dielectrics.Further, increasing the π electron delocalization of the pendant groups generally benefits the charge storage property and transistor memory behavior. Theoretical calculation reveals that the hydrogen bonding between the linkage groups and the energy alignment between polymeric dielectric and semiconductor are responsible for the observed performance differences of OTFT with different polymeric dielectrics. These results may shine light on the design of polymeric dielectrics for OTFTs with different applications.