Fluorinated polymer-grafted organic dielectrics for organic field-effect transistors with low-voltage and electrical stability

Abstract

The electrical stabilities of low-voltage organic field-effect transistors (OFETs) were improved by applying graftable fluorinated polymer (gPFS) layers onto poly(4-vinyl phenol)-based cross-linked dielectrics (cPVP). As a result, a smooth and hydrophobic surface was formed, and the dielectric film displayed a low-leakage current density. The chemisorbed gPFS groups enabled the solution processing of an overlying 5,11-bis(triethylsilylethynyl)anthradithiophene semiconductor, which formed favorable terrace-like crystalline structures after solvent annealing. The top-contact OFETs showed superior operational stability compared to cPVP-based OFETs. Hysteresis was negligible, and the off-current of the transfer curve was one order of magnitude lower than that obtained from cPVP-based OFETs. The threshold voltage shift measured after a sustained gate bias stress for 1 h decreased significantly after introduction of the hydrophobic gPFS treatment; the energetic barrier to creating charge trapping sites increased, and the trap distribution narrowed, as supported by the stretched exponential function model.