THERMAL-STABILITY OF ORGANIC ELECTROLUMINESCENT DEVICES FABRICATED USING NOVEL CHARGE TRANSPORTING MATERIALS

Novel hole and electron transporting materials have been synthesized t o improve the thermal stability of organic electroluminescent (EL) dev ices. Molecular structures of such hole and electron transporting mate rials were designed based on triphenylamine (TPA) and oxadiazole (OXD) moieties, respectively. It has been found that the resulting material s have high glass transition temperatures (Tg) over 100 degrees C and the vacuum-deposited thin films are significantly thermally stable. Fo r the two-layer EL devices using the novel hole transporting materials and the typical emitting material, tris(8-quinolinolato) aluminum, th e thermal stability has been clearly seen to depend on the Tg of the h ole transporting material; excellent thermal stability was achieved. F or the three-layer EL device using the novel electron transporting mat erial, good emission efficiency and good stability were achieved. The electron transporting materials have been also applied to the polymeri c system with polyvinylcarbazole matrix.