TRAP STATES OF TRIS-8-(HYDROXYQUINOLINE) ALUMINUM AND NAPHTHYL-SUBSTITUTED BENZIDINE DERIVATIVE USING THERMALLY STIMULATED LUMINESCENCE

The bulk trap state properties of a naphthyl-substituted benzidine der ivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq(3)) have bee n measured using thermally stimulated luminescence (TSL). The TSL spec tra for both organic materials show significant trap distributions ove r the temperature range from 8 to 300 K. Using a general order TSL exp ression, the four peaks in NPB were modeled with trap states centered from 0.20 to 0.05 eV. Alq(3) has three TSL peaks over the temperature range, with the peak at 156 K modeled as a distribution of trap states from 0.25 to 0.13 eV. For both materials, the trapping mechanism invo lves a combination of first and second order emission. NPB and Alq(3) have trap states sufficiently deep to influence the carrier transport and recombination process in bilayer organic based light emitting. (C) 1998 American Institute of Physics.