MOS 구조 기반 Ce3+이 도핑된 칼슘실리케이트 박막으로부터의 자외선-A 전계발광 연구

Abstract

The present study reports on the successful fabrication of ultraviolet (UV) electroluminescence (EL) from the Ce3+-doped CaSiO3 emitting layer in a metal-oxide-semiconductor (MOS) structure. This was achieved through a facile air annealing process of solution-based precursors. This innovative approach represents the first instance of a Ultraviolet-A (UV-A) EL device with a large-scale surface-emitting AC-driven silicon-based. The results of this study demonstrate the reproducibility of the manufacturing procedure and highlight the potential for further development of this technology. Initially, the process of optimizing annealing time, temperatures, and Ce3+ concentrations was performed, as it has been established that the electroluminescence (EL) performance of films is significantly influenced by the uniformity and concentration of the material. This step was deemed necessary in order to ensure that the resulting film would exhibit optimal EL performance. In addition to the point above, it is interesting to mention that the optimized concentration of 0.25 mol% of Ce3+-doped CaSiO3 electroluminescent (EL) device was subjected to a comprehensive analysis of its morphological characteristics through the utilization of advanced techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). This rigorous examination aimed to provide a deeper understanding of the structural and surface properties of the EL device, which could potentially lead to further improvements in its performance and efficiency. The present study reports on the deposition of electrodes on a film based on the metal-oxide-semiconductor (MOS) structure device. The device exhibited exponential voltage dependencies, which were demonstrated to be effective in a specific range of voltage. Specifically, the device showed practical efficiency when subjected to UV-A light with a peak of 355 nm and a half width of 60 nm. This efficiency was attributed to the 4f - 5d transitions from Ce3+ ion into the CaSiO3 emitting layer. Particularly, the device's voltage dependencies were observed to be above a threshold voltage of 20 Vrms and below a breakdown voltage of 36 Vrms. In the area of ultraviolet light sources, two primary options exist: discharge lamps and UV-LEDs. However, it is worth noting that both of these options possess certain limitations. Discharge lamps, for instance, tend to be bulky and cumbersome, while UV-LEDs may only emit light in a limited form, such as a spot. Despite these drawbacks, both discharge lamps and UV-LEDs remain viable options for those seeking to harness the power of ultraviolet light. In the event that one compares the UV-LED to the EL device based on MOS structure, it can be observed that the former exhibits a characteristic of high current and short lifetime, regardless of the range of UV region, become it UV-A, UV-B or UV-C. Furthermore, it is notable that the UV-LED and the EL device based on MOS structure are similar in terms of their expensive cost. Consequently, the utilization of the UV-A emitting thin film based MOS EL device is expected to be widespread across a diverse range of applications, encompassing a broad spectrum of sizes. Furthermore, the study utilized the LightTools optical simulation program to calculate both internal and external optical efficiencies. Based on the plane's properties such as refractive index, reflectance, transmittance, and absorbance the anticipated ray patterns can be explained geometrically. The remaining planes can be accounted for by the Fresnel loss. The study resulted in an internal light efficiency of 15 % and an external light efficiency of 6 %. The study of optical simulation involved quantifying light efficiency and exploring methods to enhance it by leveraging light characteristics and conducting advanced simulations with an ideal design. The application of this approach is expected to result in superior optical outcomes.