Electroluminescent devices based on polymers forming hole transporting layers, 1 - Polyimides containing o-tolidine units

摘要

Two polyimides, PI(BA-TD) and PI(6FDA-TD), based on an aromatic diamine (TD) and two aromatic dianhydrides (BA, 6FDA) were synthesized. They were characterized by viscosity, FT-IR, and X- ray photoelectron spectroscopy (XPS) measurements. XPS results reveal that the binding energy of C-1s, N-1s, and O-1s in PI(BA-TD) is lower than that in PI(6FDA-TD). The synthesized polyimides form stable and homogeneous thin films on an ITO electrode, functioning as good hole transporting materials for organic electroluminescent (EL) devices. The double-layered EL devices consisting of a hole transporting layer df these polyimides and an emitting layer of the tris(8-quinolinolato)aluminium complex exhibit a peak emission wavelength in the bright green at 521 similar to 525 nm. Furthermore, a maximum luminance of 97 cd/m(2) was achieved at a voltage of 15 V with a current density of 192 mA/cm(2) for the EL device using PI(BA-TD) as a hole transporting layer. The phenomenon of an extended luminance of these EL devices was also found when a voltage higher than 15 V was applied. [References: 64]