CONTROLLING SCHOTTKY ENERGY BARRIERS IN ORGANIC ELECTRONIC DEVICES USING SELF-ASSEMBLED MONOLAYERS

We demonstrate tuning of Schottky energy barriers in organic electroni c devices by utilizing chemically tailored electrodes. The Schottky en ergy barrier of Ag on poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenyl ene was tuned over a range of more than 1 eV by using self-assembled m onolayers (SAM's) to attach oriented dipole layers to the Ag prior to device fabrication. Kelvin probe measurements were used to determine t he effect of the SAM's on the Ag surface potential. Ab initio Hartree- Fock calculations of the molecular dipole moments successfully describ e the surface potential changes. The chemically tailored electrodes we re then incorporated in organic diode structures and changes in the me tal/organic Schottky energy barriers were measured using an electroabs orption technique. These results demonstrate the use of self-assembled monolayers to control metal/organic interfacial electronic properties . They establish a physical principle for manipulating the relative en ergy levels between two materials and demonstrate an approach to impro ve metal/organic contacts in organic electronic devices.