High brightness alternating current electroluminescence with organic light emitting material

We report on an alternating current (AC) organic electroluminance (EL) device with high brightness of over 1500 cdm−2 and very low threshold voltage for the onset of AC luminance (10 V). The device consists of organic layers enclosed in a pair of either silicon dioxide (SiO2) or hafnium dioxide (HfO2) insulating dielectric layers. We observe internal charge carrier generation and luminance due to charge carrier recombination within the device under the AC drive without charge injection. We compare AC-EL demonstrated for the two devices and show that the threshold voltage for the onset of luminance can be significantly lowered using high dielectric constant (κ) HfO2 insulating layers. Further, we discuss the limitations of internal charge carrier generation and the device performance supported with the results from time resolved measurements.