Abstract
We investigated the properties of alternating current (AC)-driven electroluminescence from (Ba0.4Ca0.6)TiO3:Pr3+ diphase polycrystal-based device. The results of crystal phases and micrographs, and the symmetrical dual emissions in one AC cycle, indicate the spontaneous formation of a dielectric/phosphor/dielectric sandwich microstructure in (Ba0.4Ca0.6)TiO3:Pr3+. The electroluminescent device emits a red light of 617 nm, which is attributed to the 1D2-3H4 transition of Pr3+ in the phosphor phase. At a fixed AC frequency, the intensity of electroluminescence exhibits a steep enhancement when applying an increased driving electric field that is beyond a threshold. In a fixed driving electric field, the intensity of electroluminescence shows a rapid rise at low frequencies, but reaches saturation at high frequencies. Based on a double-injection model, we discussed systematically the electroluminescent processes in a whole cycle of AC electric field, which matched well with the experimental data. Our investigation is expected to expand our understanding of such a diphase electroluminescent device, thereby promoting their applications in lighting and displays.
Highlights
Since the electroluminescence was first discovered in 1936 in the ZnS-based device [1], a range of products based on alternating current (AC) powder electroluminescence have been developed and applied, including the typical application in flat-panel displays and solid-state lighting [2,3,4,5]
Their research indicated that a series of dielectric/phosphor/dielectric sandwich architectures was formed spontaneously on a micrometer scale during the material synthesis through a conventional solid-state reaction, which greatly simplifies the manufacturing processes of electroluminescent devices and raises the possibility of developing novel devices [12]
To the best of our knowledge, there have not been related reports that elucidate the electroluminescent process of such a diphase system during a complete AC cycle, which hinders the promotion of application to Materials 2017, 10, 565; doi:10.3390/ma10050565
Summary
Since the electroluminescence was first discovered in 1936 in the ZnS-based device [1], a range of products based on AC powder electroluminescence have been developed and applied, including the typical application in flat-panel displays and solid-state lighting [2,3,4,5]. The dielectric layers are used to enhance the resistance of devices to a high electric field and to provide the initial injection electron into phosphor layers. Zhang et al subsequently ascribed the injection of initial electrons from dielectric grain to phosphor grain to the Schottky emission of the interface state in the high electric field [13].
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