Nano Structure and Novel Charging Materials of the Small Molecule Based OLED Devices

Abstract

This work introduces the process of fabricating a conventional bilayer-structured small molecule based Organic Light Emitting Diode (OLED) device by vacuum thermal deposition technology using a Kurt J. Lesker deposition machine. The system was calibrated carefully by determining the tooling factor of all the materials that were used.
The indium-tin-oxide (ITO) coated glass substrates with a thin layer of polycarbonate (PC) template overlaid were supplied by Dr. Etienne Ferain of Université catholique de Louvain, Belgium. In the PC film, an array of consistently structured, randomly distributed nanopores with diameter up to 110 nm were produced and used as a mask to fabricate the nano-OLEDs. The device was then tested and compared to a normal scaled OLED device. To further prove the fabrication of nano-OLEDs, images of Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) measurements were presented.
Finally, a set of iridium complexes synthesized by Professor Martin Bryce‟s group in the Chemistry Department of Durham University were spin-coated onto the ITO/Glass substrate to make an OLED device. Such complexes, while in devices, behave as the electrolyte. When a Voltage bias was applied to a system with a heavy cation and light anion, the light anions will flow toward the anode to form a built-in voltage across the system. The charge carriers injecting barrier is thus lowered to enhance the electroluminescence (EL) performance of the OLED device. Devices made from 5 different iridium complexes were produced and measured in the course of this work. The highest efficiency achieved was 7.8 cd/A @ 9V with a simple
aluminum / iridium complex / Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) / ITO structure.