Stable Low Voltage Organic Light-Emitting Diode Using Insulating Polymer/Conducting Polymer Blends

Organic light-emitting diodes (OLEDs) utilizing the blend of doped polyaniline (PANI-DBSA) and aromatic polyimide (PMDA-ODA PI) as a hole transport layer (HTL) were successfully fabricated. Tris(8-hydroxyquinolinato aluminum) (Alq(3)), indium-tin oxide (ITO), and aluminum (Al) were used as a lumophore, transparent anode, and stable cathode, respectively. The charge injection of the OLEDs with the softbaked and imidized HTL was started at ca. 4 Vdc and 3 Vdc, whereas the turn-on voltage was ca. 5 Vdc for the OLED with the imidized film as a HTL. The electroluminescent (EL) spectra of both OLEDs were almost the same as those of photoluminescence (PL) of the HTL/Alq(3) films with marginal shift toward higher energy.