Blue Emitting Thin-Film Electroluminescence Devices Using a Valence Controlled Rare-Earth Luminescence Centers

薄膜电致发光（EL）显示器是一种固态显示器件，具有发光、分辨率高、视角宽、运行速度快等优点，但显示颜色仅限于黄橙色。因此，彩色薄膜EL显示器正成为下一个重要的开发目标。为此，强烈需要开发彩色薄膜EL磷光体，特别是发蓝光的EL磷光体。本论文研究了以稀土为发光中心的蓝光薄膜电致发光材料.研究了SrS：Eu，F薄膜中Eu发光中心的带电状态。在低浓度时，Eu^2+心存在，而在高浓度时，Eu^2+和Eu^3+心共存。Eu^<2+>和Eu^<3+>中心均显示红色电致发光.对ZnS晶格中Eu发光中心的价态控制进行了测试。众所周知，Eu^<3+>发光中心产生红色荧光， ...更多信息 （4f）^6电子组态的f-f跃迁引起的EL发射。相反，ZnS晶格中的Eu^<2+>由于（4f）^6（5d）-（4f）^7跃迁而产生蓝色电致发光。为了控制Eu离子的价态，我们研究了几种共活化剂。而Eu掺杂的ZnS薄膜由于Eu^2+中心的存在，没有显示出蓝光发射.研究了ZnS：Tm^<3+>蓝色荧光粉的电致发光和光致发光特性. T^<3+>中心的光致发光激发机制可归因于ZnS基质到Tm^<3+>中心的非辐射能量转移。相反，EL激发机制是由于热电子的碰撞激发而不是能量转移。EL中蓝光发射相对低效率的原因是较低的^3F_4态的激发比较高的^1G_4态的激发占优势.锌和碱土金属硫化物存在一些基本问题，如稀土离子溶解度低。电荷补偿等。为了解决这些问题，我们采用UP Y_2O_2S作为三价稀土离子的基质材料。讨论了多源沉积法（MSD）制备的Y_2O_2S薄膜的性质。发现稀土掺杂Y_2O_2S具有良好的电致发光性能

Thin-film Electroluminescent(EL)display panel is a solid state device and has many advantages of light emitting, high resolution, wide viewing angle and high operating speed, but color of display is limited to yellowish-orange. Therefore, color thin-film EL displays are becoming the next important target to be developed. For this purpose, a development of color thin film EL phosphors, especially, blue emitting EL phosphors, is strongly required. In this work, we studied blue emitting thin-fijm EL phosphors using a valence controlled rare-earth luminescence centers.1. We have studied the charging state of Eu luminescent centers in SrS : Eu, F thin films. At lower Eu concentration, Eu^<2+> center exist, but at higher concentration over 0.6 mol%, both Eu^<2+> and Eu^<3+> centers coexist. Both Eu^<2+> and Eu^<3+> centers showed red EL emission.2. Valence control of Eu luminescent centers in the ZnS lattice has been tested. It is well known that Eu^<3+> luminescent centers give rise to red … More EL emission due to f-f transitions of (4f)^6 electron configuration. On the contrary, Eu^<2+> in the ZnS lattice give rise to blue EL emission due to (4f)^6 (5d)-(4f)^7 transitions. To control valence of Eu ions, we have investigated several co-activators. However, Eu-doped ZnS thin-films prepared did not show blue emission due to Eu^<2+> centers.3. The EL and PL characteristics of blue emitting ZnS : Tm^<3+> phosphors have been studied. The PL excitation mechanism of T^<3+> centers is attributable to the non-radiative energy transfer from the ZnS host to the Tm^<3+> centers. On the contrary, the EL excitation mechanism is due to impact excitation by hot electrons rather than energy transfer. The cause for the relative inefficiency of blue emission in EL is that the exciation of the lower lying ^3F_4 state is dominant compared with that of the higher lying ^1G_4 state.4. Zinc- and alkaline-earth sulfides have some fundamental problems, such as low solubility of rare-earth ions. electric charge compensation etc. . To solve such problems, we took UP Y_2O_2S as a host materials for trivalent rare-earth ions. We discussed the properties of Y_2O_2S thin films prepared by multi-source-deposition (MSD) method. It has been found that rare-earth doped Y_2O_2S shows efficient EL emission Less