Molecular light-emitting diodes using quinquethiophene Langmuir-Blodgett films

We report extended studies on electroluminescence from molecularly thin semiconducting Langmuir-Blodgett films of quinquethiophene. The effect of the thickness of active layer and cathode electrode material has been investigated. From all these devices, greenish electroluminescence (visible in a dark room) has been observed with quantum efficiencies of the order of 10-3%. Even five or nine layers of Langmuir-Blodgett films yield the same luminance as thicker films. The electroluminescence spectrum showed a profile identical to the photo- luminescence spectrum