| Organic light-emitting diodes (OLEDs) have been intensively studied due to their emerging applications in flat panel display technologies. The motivation of the present research has been the desire to (a) explore new routes to OLED functional layers with rigorous control of layer properties; (b) probe the effects of OLED anode-hole transport layer interfacial energetics on charge injection, luminous efficiency; (c) acquire micron-scale multicolor OLED pixels for potential high resolution OLED display application; (d) better understand and further improve charge injection into molecular and macromolecular solids by designing and implementing novel OLED anode materials. In the first part, a spin-coating/siloxane cross-linking approach has been applied to OLED charge transport layers which provides a high throughput route to robust, pinhole-free, adherent thin films with covalently interlinked, glassy structures (Chapter 2). In anode-hole transport layer contact study (Chapter 3), it is shown that integrity of electrode/organic interfacial contact is crucial to the performance and stability of organic light emitting diodes (OLEDs). It is demonstrated that self-assembled or spincoated nm-scale thick silane derived hole transport layer on ITO can effectively prevent de-wetting of the vapor deposited TPD hole transport layers (Chapter 3), leading to significantly enhanced light output (15,000 cd/m2), luminous efficiency (1.2%), and thermal stability (up to 110°C). In applying soft lithography techniques to OLED micro-patterning, we designed and implemented high temperature micro-contact printing, which readily affords pixel features down to 1.0 micron dimensions, and which, by virtue of the length scale-dependent carrier tunneling through SAM structures, affords tenability in luminescence patterns (Chapter 4). To facilitate hole injection at anode side of OLED, MOCVD derived, highly transparent, high work function thin film TCO materials is synthesized and employed as OLED anodes (Chapter 5). Besides exhibiting high electrical conductivities (1000–3300 S/cm) and outstanding optical transparencies (>90%), these TCO films possess unusually high work functions (5.2–6.1 eV vs. 4.7 eV for ITO). OLED devices fabricated with these materials as anodes exhibit electroluminescence performance comparable to or better than ITO-based devices. |
