A direct-current-driven inorganic electroluminescent device using a rare-earth doped ZnO layer

Abstract

Directcurrent (dc)driven inorganic electroluminescent (EL) devices were fabricated with rareearth (RE) doped ZnO as the light emitting layer (RE = Tm, Eu). The suitability of several polycrystalline materials for the substrate was examined. Among the examined materials of yttriastabilized zirconia (YSZ), alumina (Al 2 O 3 ) and magnesia (MgO), YSZ was preferable with respect to the similarity of the thermal expansion coefficient and the chemical inertness with ZnO. On the other hand, the chemical affinity of zirconia with RE 3+ became a problem. When RE = Eu, a byproduct phase of Eu 2 Zr 2 O 7 was formed during heattreatment at a high temperature. Coating a MgO thinlayer on YSZ (MgOcoated YSZ) did not alleviate the formation of Eu 2 Zr 2 O 7. The dcdriven EL devices fabricated on the YSZ and MgOcoated YSZ substrates successfully revealed EL from the bare REdoped ZnO layers between the electrodes. A sharp line emission due to Tm 3+ and Eu 3+ was obtained from Tm 3+  and Eu 3+ doped ZnO on YSZ, respectively, whereas the REdoped ZnO layers formed on MgOcoated YSZ emitted a broad luminescence due to the luminescent defects in ZnO.

Electroluminescence of intrashell transitions in Eu doped single ZnO nanowires

“…This approach was used for thinfilm electroluminescence (TFEL) devices in varieties of complexity, thus it is still limited to planar morphologies. In all previous works, doping was performed during growth to achieve the TFEL final structure [17][18][19][20][21][22]. However, such a method is difficult to be used in case of ZnO NWs, because of the low solubility limit of the dopants in the NW material during the frequently applied vapor-liquid-solid (VLS) method [23][24][25][26][27][28].…”