Spin polarized electrodes for organic light emitting diodes

Light emission from organic semiconductors is attracting considerable attention nowadays. In conventional organic light-emitting diodes (OLED) the optical emission is governed by the radiative decay of singlet excitons, while triplet excitons can lead to some delayed fluorescence or phosphorescence. Controlling the spin statistics by injecting and transporting carriers with defined spin orientation can amplify a chosen electronic transition increasing the device efficiency or changing the emission spectral band. Electro-optical characterizations of OLEDs based on Alq3 electroluminescent material are presented for both normal and spin polarized electrode configurations. Epitaxial thin films of the manganite La_0.7Sr_0.3MnO₃ were used as spin polarized (SP) hole injector, while iron and cobalt films were used as SP electron injecting electrode. Our results demonstrate the suitability of ferromagnetic metals as electrodes in OLED opening new possibilities for OLED operation.