Multicolor and near-infrared electroluminescence from the light-emitting devices with rare-earth doped TiO_2 films

摘要

We report on multicolor and near-infrared electroluminescence (EL) from the devices using rare-earth doped TiO_2 (TiO_2:RE) films as light-emitting layers, which are ascribed to the impact excitation of RE~(3+) ions, with the EL onset voltages below 10 V. The devices are in the structure of ITO/ TiO_2:RE/SiO_2/Si, in which the SiO_2 layer is ～10nm thick and RE includes Eu, Er, Tm, Nd, and so on. With sufficiently high positive voltage applied on the ITO electrode, the conduction electrons in Si can tunnel into the conduction band of SiO_2 layer via the trap-assisted tunneling mechanism, gaining the potential energy ～4 eV higher than the conduction band edge of TiO_2. Therefore, as the electrons in the SiO_2 layer drift into the TiO_2:RE layer, they become hot electrons. Such hot electrons impact-excite the RE~(3+) ions incorporated into the TiO_2 host, leading to the characteristic emissions.