Abstract
We report on visible and near-infrared (NIR) electroluminescence (EL) from the device based on the TiO2/p+-Si heterostructure, in which the TiO2 film is composed of anatase and rutile phases. As the device is applied with sufficiently high forward bias with the positive voltage connecting to p+-Si, the visible EL peaking at ∼600 nm along with the NIR EL centered at ∼810 nm occur simultaneously. It is proposed that the oxygen vacancies in the anatase TiO2 and Ti3+ defect states in the rutile TiO2 are the responsible centers for the visible and NIR EL, respectively.
Highlights
TiO2 is a multifunctional oxide semiconductor that has been studied for a long time in the fields of dye-sensitized solar cells and photo-catalysis.[1,2,3,4] The most common phases of TiO2 are namely anatase and rutile, with the bandgap of ∼3.2 and 3.0 eV, respectively
Such two-phased TiO2 film is formed by oxidation of the Ti film with prior etching in the H2O2 solution
In the X-ray diffraction (XRD) pattern of the TiO2 film formed by the oxidation of the etched Ti film, besides the pronounced peaks corresponding to the anatase phase, a few of minor peaks that can be indexed into rutile phase appear
Summary
TiO2 is a multifunctional oxide semiconductor that has been studied for a long time in the fields of dye-sensitized solar cells and photo-catalysis.[1,2,3,4] The most common phases of TiO2 are namely anatase and rutile, with the bandgap of ∼3.2 and 3.0 eV, respectively. The luminescence from TiO2 should essentially originate from defect-related energy levels.[5,6,7] In our earlier reports, we have realized the visible electroluminescence (EL) from the anatase TiO2/p+-Si heterostructured device.[8,9] Such EL originates from the radiative recombination of oxygen-vacancy-related self trapped excitons (STEs). We have realized the visible and NIR EL from the TiO2/p+-Si heterostructured device, in which the TiO2 film is composed of anatase and rutile phases. Such two-phased TiO2 film is formed by oxidation of the Ti film with prior etching in the H2O2 solution. We believe that this work offers new evidence to understand the defect-related luminescence in TiO2 and opens up new possibility to develop the silicon-based light-emitting devices using oxide semiconductors
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