Abstract
Chemically stable and easily printable inorganic surface-emitting devices are essential for portable, disposable, outdoor-safe, and wearable information display devices. However, inorganic electroluminescent devices with both chemical stability and printability have never been realized. We present the first report of an oxide-nanocrystalline powder-type self-emitting device without both capping and dispersion treatments. The Ca0.6Sr0.4TiO3:Pr nanocrystal was prepared by a hydrothermal synthesis method under supercritical water conditions. The red light-emitting electroluminescence intensity increased with an increase in the driving voltage. The starting electric field for electroluminescence generation is sufficiently low (6.9 × 104 V cm−1). The proposed electroluminescent device is achieved by minimizing the voids into the inside of the light-emitting layer and the interface between the light-emitting and insulating layers by using nanometer-sized oxide-phosphor-crystals. The oxide-nanocrystal electroluminescent device will be developed into future powder-type surface-emitting devices that may contribute in inventing numerous applications, such as outdoor information displays and wearable information terminals.
Highlights
Nanocrystals with diameters ranging from one to several tens of nanometers are characterized by properties such as large specific surface area and surface anomalous morphology, and have been utilized in various fields
The phosphor Ca0.6Sr0.4TiO3:Pr (PCSTO) nanocrystal without both capping and dispersion treatments was sprinkled on an indium tin oxide (ITO)-coated glass substrate to fit within a circular-hole-punched insulating adhesive tape with a diameter of 3 mm and a thickness of 40 μm [Fig. 1(b), upper left]
No light emission was performed, and no current was generated by applying a dc bias. These results suggest that the nanocrystal electroluminescent devices (ELDs) emits red-electroluminescence triggered by the hot electron injection from the interface between the PCSTO/BTO layers
Summary
Nanocrystals with diameters ranging from one to several tens of nanometers are characterized by properties such as large specific surface area and surface anomalous morphology, and have been utilized in various fields. Among the promising optoelectronic devices, inorganic electroluminescent devices (ELDs) can produce surface light emissions that can be stably operated by applying a voltage. After the discovery of the epitaxial-thin-film-type oxide-phosphor Ca0.6Sr0.4TiO3:Pr (PCSTO),[10] thin-film-type ELD driven by a low electric field of 9 × 104 V cm−1 was realized by using the PCSTO as a light-emitting layer.[11]. PCSTO is one of the most promising materials for oxide ELDs, which has an ABO3 perovskite-type structure.[12]. Almost all ceramic capacitors and piezoelectric ceramics are made of perovskite-type oxide because these excellent functionalities are obtained together with chemical stability.[21]. Perovskite-type oxide ELDs have the potential to dominate the surface-emitting device market as was the case with multilayered ceramic capacitors and piezoelectric ceramic devices Oxide ELDs were recently improved by focusing on the miniaturization of device components and the actualization of the direct current operation.[27–30] perovskite-type oxide ELDs have the potential to dominate the surface-emitting device market as was the case with multilayered ceramic capacitors and piezoelectric ceramic devices
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