Effects of concentration and local structure on charge trapping in polymer electrets with amine-based substituents.

Thin film polymer dielectrics with controllable electronic properties are of considerable interest for applications in organo-electronic systems. We use amine-based moieties in thin film polystyrene dielectrics to modify electron and hole trap states and densities. When chemically bound to polymers and also when introduced as free additives, these moieties induce changes in static potential differences that modify the behavior of adjacent electronic materials. For example, N,N’-diphenyl-N,N’-di-p-tolybenzene-1,4-diamine in polystyrene exhibited threshold voltage shifts up to ΔV_th=O(50V) after application of static electric fields as measured in pentacene-based OFETs. Films with free additive concentration in the range of 1-3% showed a strongly concentration dependent stability in V_th, in contrast to polystyrene systems with tethered amines. Stability is higher at lower amine concentrations suggesting clustering of additives is an important effect in these systems.