Improved Static Charge Stability from Fluorinated Polystyrenes in Multilayer Polystyrene Electrets*

Thin film polymer electrets are of considerable interest for applications in organo-electronic systems such as piezoelectrics for energy harvesting and nonvolatile field effect transistors as memory, sensing, and logic elements. Copolymerized combinations of substituted styrenes can be used to produce multifunctional polymers with tunable electronic and structural properties. In multilayered dielectric stacks, these modified polymers demonstrate stable and controlled effects on adjacent semiconductors. Poly(3-trifluoromethylstyrene) and related copolymers exhibit layer position-dependent effects on the initial performance of thin film pentacene-based transistors, more consistent performance compared with unmodified polystyrene dielectrics, and large threshold voltage shifts (ΔV_th= O(30 V)) after charging by application of static electric fields. In-situ dynamic measurements of transistor properties show these trifluoromethylated materials confer greater stability of electronic effects in terms of the magnitude of effect, biasing from device operation, and response to multiple charging and discharging cycles.