DETERMINATION OF ELECTROAFFINITY AND IONIZATION-POTENTIAL OF CONJUGATED POLYMERS VIA FOWLER-NORDHEIM TUNNELING MEASUREMENTS - THEORETICAL FORMULATION AND APPLICATION TO POLY(P-PHENYLENE VINYLENE)

In this paper we present a method to obtain the electroaffinity and th e ionization potential of conjugated polymers via Fowler-Nordheim tunn eling current measurements. The method allows the measurement of the e lectroafinity and ionization potential for a sandwich type device! whe n the barriers at both sides of the polymer are different. The advanta ge of this method is that barrier height, the electroaffinity, and the ionization potential are obtained independent of the polymer film thi ckness and the electron (or hole) effective mass. We have used the pro posed methodology to obtain the barrier heights and electroaffinity of poly (p-phenylene-vinylene) (PPV) in Metal/Polymer/Metal sandwich str uctures. For the present case the electrodes (Al/Au, Al/Ga, Al/In, Al/ Sn) used lead only to electron and not hole tunneling current, thus on ly the electroaffinity has been obtained. The experimental value for t he electroaffinity of PPV is of 3.87+/-0.04 eV. (C) 1996 American Inst itute of Physics.