title: Change in electronic states in the accumulation layer at interfaces in a poly(3-hexylthiophene) field-effect transistor and the impact of encapsulation.
abstract: The electrical properties of organic field-effect transistors (OFETs) are largely determined by the accumulation layer that extends only a few molecular layers away from the gate dielectric/organic semiconductor interface. To understand degradation processes that occur within the device structure under ambient conditions, it is thus essential to probe the interface using an architecture that minimizes the effects of bulk transport of contaminating species through upper layers of material in a thick film device. Using FETs designed with multiple voltage probes along the conducting channel and an ultrathin film of the active material, we found that the charge carrier density and the FET mobility decrease, and further, the contact and channel properties are strongly correlated. FET devices prepared with an ultrathin film of P3HT become significantly contact limited in air due to a hole diffusion barrier near the drain electrode. Encapsulation of the device with a layered organic/inorganic barrier material consisting of parylene and Al(2)O(3) appreciably retarded diffusion of molecular species from ambient air into P3HT.
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States. bp288@cornell.edu
authors.forename: Byoungnam
authors.initials: B
authors.lastname: Park
authors.forename: Y J
authors.initials: YJ
authors.lastname: Kim
authors.forename: Samuel
authors.initials: S
authors.lastname: Graham
authors.forename: Elsa
authors.initials: E
authors.lastname: Reichmanis
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D004553:Electric Conductivity; D006046:Gold / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D013876:Thiophenes / Q000737:chemistry*; D014173:Transistors, Electronic; D014992:Xylenes / Q000737:chemistry
chemical_list: D011108:Polymers; D013876:Thiophenes; D014992:Xylenes; C507295:poly(3-hexylthiophene); C011055:parylene; D006046:Gold; D000537:Aluminum Oxide