The spin-polarized organic light emitting diode

We report magnetic field, voltage and temperature dependent studies on recently realized spin-polarized organic light emitting diode (spin-OLED) with ferromagnetic (FM) electrodes that acts as a bipolar organic spin valve (OSV). In the double-injection regime the device shows ∼1% spin-valve related magneto-electroluminescence (MEL) response that follows the FM electrode coercive fields. In stark contrast to the properties of homopolar OSV devices, both the MEL and magneto-conductivity responses in the double-injection regime are practically bias voltage independent, and their temperature dependence follows that of the FM electrode magnetization. Careful comparative studies of devices with various FM/non-FM electrodes rule out the possibility that the observed MEL is due to the effect of stray magnetic fields associated with the FM electrodes. The spin-OLED behavior is explained by the spin-aligned space charge-limited current operation upon reaching double-injection conditions during bipolar operation.