Supramolecular Assembly Strategies Using Alternate Adsorption of Polyelectrolytes: Applications in Pled And Lc Display D

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AL 35294-1240

Max Planck Institute for Polymer Research, Mainz, GERMANY D-55021 Niigata University, Dept. of Electrical Eng., Niigata, JAPAN 950-21

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ABSTRACT We present work on the modification, processing, and analysis of ultrathin films for display devices primarily using the supramolecular assembly strategy. This involves the use of various molecular assembly techniques (organic, polymer, metal) in which layer order and functionality is achieved at defined length scales approaching that of ultrathin films (a few to several hundred nm thicknesses). The use of alternate polyelectrolyte deposition (APD) is primarily investigated in ultrathin films that have significance in the fabrication of display devices. The first application involves modifying a polymer light emitting diode (PLED) device fabricated using the ITO/MEH-PPV/Ca protocol with polyaniline derivatives. The second is the use of the "command layer" amplification concept and photo-induced alignment using polarized light with ultrathin films of azo dye/polyelectrolytes in a hybrid liquid crystal (LC) cell configuration. Both strategies rely on the use of surface sensitive spectroscopic and microscopic techniques to correlate device performance with layer ordering at the molecular level. The concept of functional ultrathin layers for device fabrication and modification is emphasized.

INTRODUCTION The advent of opto-electronic devices derived from organic and polymeric materials has resulted in a number of configurations both in constitution (synthetic), ordering (processing), and operation (devices). While ultrathin film processing techniques, e.g. spin-coating and vacuum evaporation of molecules has been considered traditional protocol, a number of molecular, macromolecular, and supramolecular assembly approaches involving deposition on a layer by layer basis has afforded unique architectures at the nanoscale regime, often not possible with one technique alone. A number of these include Langmuir-Blodgett-Kuhn (LBK) film deposition, self-assembly of monolayers (SAM), alternate polyelectrolyte deposition (APD), and combinations thereof. It is important to develop strategies where the use of organic materials in the microelectronics and display technologies can be combined with the more traditional processing protocols. Ultrathin organic and polymer films (a few to several hundred nm thicknesses) analyzed by a number of surface sensitive spectroscopic and microscopic techniques provides that important link. At these length scales, it is possible to integrate functionality or modify these devices without compromising traditional processing protocols such as vacuum evaporation or photolithography.

415 Mat. Res. Soc. Symp. Proc. Vol. 558 ©2000 Materials Research Society

In this report, we present our work on the modification of display devices primarily using the APD technique.[I] We have used the term supramolecular assembly to denote different types of processing involved within the device layer configuration and the molecular ordering that is achieve