Abstract In this paper, we report an improved luminous efficiency of a direct-current-driven electroluminescent (EL) device using ZnS powder by controlling electron and hole injection barriers. The emission layer was fabricated by screen-printing of an EL paste using Cu-coated ZnS particles on a transparent conductive indium–tin-oxide electrode. The device was completed by stacking an Al thin film on the emission layer by thermal evaporation. We applied various forming voltages to investigate the current–voltage–luminescence characteristics of the device. An abrupt change in current during the forming process was caused by variation of the electron-blocking barrier toward the anode. The hole-injection barrier from the anode to the emission layer increased with the forming voltage. The obtained results indicated that the hole-injection barrier to the emission layer can be lowered by inserting materials with a low highest-occupied-molecular-orbital (HOMO) energy level between the anode and emission layer. We achieved a brightness enhancement of 29% by employing a thin film of poly-N-vinyl carbazole with a HOMO level of −5.6 eV as a hole-injection layer on the anode. We believe that the presented results will guide further studies for efficiency improvement of EL devices using powder particles applicable to next-generation lighting and displays.

中文翻译：

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硫化锌粉末制备的直流驱动电致发光器件的亮度增强

摘要 在本文中，我们报告了通过控制电子和空穴注入势垒来提高使用 ZnS 粉末的直流驱动电致发光 (EL) 器件的发光效率。发射层是通过在透明导电铟锡氧化物电极上使用涂铜的 ZnS 颗粒丝网印刷 EL 糊剂来制造的。该器件是通过热蒸发在发射层上堆叠铝薄膜来完成的。我们应用各种形成电压来研究器件的电流-电压-发光特性。形成过程中电流的突然变化是由朝向阳极的电子阻挡势垒的变化引起的。从阳极到发射层的空穴注入势垒随着形成电压的增加而增加。所得结果表明，通过在阳极和发射层之间插入具有低最高占据分子轨道 (HOMO) 能级的材料，可以降低对发射层的空穴注入势垒。通过使用 HOMO 能级为 -5.6 eV 的聚 N-乙烯基咔唑薄膜作为阳极上的空穴注入层，我们实现了 29% 的亮度增强。我们相信，所呈现的结果将指导进一步研究，以使用适用于下一代照明和显示器的粉末颗粒来提高 EL 设备的效率。6 eV 作为阳极上的空穴注入层。我们相信，所呈现的结果将指导进一步研究，以使用适用于下一代照明和显示器的粉末颗粒来提高 EL 设备的效率。6 eV 作为阳极上的空穴注入层。我们相信，所呈现的结果将指导进一步研究，以使用适用于下一代照明和显示器的粉末颗粒来提高 EL 设备的效率。