Abstract
Researches on conjugated conducting polymers have been actively pursued in the last two decades due to the scientific and industrial interests on their unique optical and electronic properties. One of the recent interesting focuses is on the electroluminescence property of conjugated polymers. Polyanilines, with a relative low oxidation state and a rather light coloring in its conductive form, has been demonstrated to be a good hole-transport material in its neutral form and also as a good candidate material for transport positive electrode.The major drawbacks of using polyanilione as a hole-transport layer is the relative poor adhesion of polyaniline to ITO glass electrode, which often resulted in the peeling off of the polyaniline coating and therefore led to the poor reliability and shorter life of the corresponding LED (Light Emitting Diode) devices.To prepare a better adhered and more reliable polyaniline hole-transport layer we have devised a new reaction treatment to convert polyaniline matrix into a highly cross-linked matrix, which is based on our recently discovered concurrent reduction and substitution chemistry for polyanilines.Heeger et al. demonstrated that when doped PAni or combination of doped PAni and ITO was used as the transparent anode for a polymer LED of MEH-PPV, the device performance can be significantly improved. Although a HOMO value of 4.8 eV had been assigned for the polyaniline materials, the detailed information about how the value was obtained was however lack of. Nor the origin of the HOMO data (whether associated with either doped PAni or undoped PAni) was specified. Furthermore, the LUMO and bandgap information were also not reported. Our preliminary results indicated that the HOMO, LUMO, and bandgap of the undoping emeraldine base form of PAni is 4.9, 3.4, and 1.5 eV