Application of polyaniline (emeraldine base, EB) in polymer light-emitting devices

We report the fabrication of several multilayer light-emitting-diode (LED) devices based on a novel conjugated polymer, poly(2,5-dihexadecanoxy phenylene vinylene pyridyl vinylene) (PPV-PPyV), involving the use of polyaniline (emeraldine base, EB) as an insulating layer between the emissive polymer layer and the electrodes. In all the above devices with various configurations ('3-layers', '4-layers-1', '4-layers-2' and '5-layers'), only the symmetrically configured a.c. light-emitting (SCALE) ('5-layers') device shows the capability of operating in both forward and reverse bias modes and in an a.c. mode. The SCALE devices have a typical turn-on voltage of about 4-6 V and work well under both forward and reverse bias modes. It is important to note that the total resistance (R = V/I) of the four devices at any given applied potential decreases as the number of insulating polymer layers increases, suggesting that the nature of the electrode/polymer interface plays a critical role in determining the characteristics of the devices.