LANGMUIR-BLODGETT-FILMS OF CONJUGATED POLYMERS - ELECTROLUMINESCENCE AND CHARGE-TRANSPORT MECHANISMS

This paper reviews and reports our work on the development of polymeri c light-emitting diodes (LED's) based on Langmuir-Blodgett (LB) films. We have used LB deposition technique as a tool to fabricate de and ac LED's with a precise thickness ranging from a few molecular layers to tens of layers. In de LED's, we have shown that as few as three EB la yers of active polymer can yield the same luminance as the thicker one s, With the advantage of LB deposition technique to fabricate heterost ructure (multilayer) devices, we have used carrier transporting materi als and carrier blocking LB films to control and balance the charge in jections in de LED's, The frequency dependence of (multilayered) ac LE D's has been studied and moderately high-frequency (20 kHz) electrolum inescence (EL) intensity has been obtained, From the transient EL meas urements, the role of interfaces in polymeric LED's has been emphasize d and the operation mechanism of LED's has been discussed.