Orientation-controlled organic electroluminescence of p-sexiphenyl films

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Abstract
A multilayered electroluminescent device was constructed with epitaxially oriented films of p-sexiphenyl with its molecular axis lying or standing next to the substrate surface. The films with the lying and standing orientations were prepared by vapor deposition onto the KCl (001) surface kept at 20 and 150 °C, respectively. After successive depositions of electron-transport layer and Al cathode, the films were removed from the KCl substrate and transferred on an indium tin oxide coated glass anode. The cell with lying molecules emitted a higher electroluminescence with a narrowed spectrum at remarkably low driving voltages, as compared to one with standing molecules. This electroluminescent behaviors depend upon anisotropic distribution of the polarized emission light as well as efficiency of the carrier transport in the ordered molecular arrays with different orientation modes.