Phosphorescent organic light emitting diodes (PHOLEDs) have been fabricated with structure of indium tin oxide/MoO 3 doped 4,4′- N,N' -dicarbazole-biphenyl (CBP) 30 nm/tris(4-carbazoyl-9-ylphenyl)amine 10 nm/CBP doped with tris(2-phenylpyridine)iridium(III) (CBP:Ir(ppy) 3 ) x /bathocuproine 50 nm/LiF 1 nm/Al, where x = 2.5, 5, 10, and 20 nm, respectively. The current efficiency (CE) of device with x = 10 nm is higher than those with x = 2.5 and 5 nm, mostly because the width of exciton formation zone (5.7 nm) with x = 10 nm is larger than those (2.5 and 5 nm) with x = 2.5 and 5 nm. However, the current density with x = 10 nm decreases than those with x = 2.5 and 5 nm at a certain driving voltage, since the ~ 4.3 nm CBP:Ir(ppy) 3 accommodating no exciton formation with x = 10 nm plays a role of transporting holes, raising ohmic loss of hole and thereby increasing driving voltage. When x increases from 10 to 20 nm, the width of exciton formation zone rises from 5.7 to 6.8 nm with CE almost unchanged, and the current density decreases as a result of increased ohmic loss of hole. The current research is useful to develop high-efficiency and low-driving voltage PHOLEDs.

中文翻译：

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激子形成区的宽度决定了磷光有机发光二极管的性能

磷光有机发光二极管 (PHOLED) 已制成具有氧化铟锡/MoO 3 掺杂的 4,4'-N,N'-二咔唑-联苯 (CBP) 30 nm/tris(4-carbazoyl-9-ylphenyl) 结构胺 10 nm/CBP 掺杂三（2-苯基吡啶）铱 (III) (CBP:Ir(ppy) 3 ) x /浴铜灵 50 nm/LiF 1 nm/Al，其中 x = 2.5、5、10 和 20 nm ， 分别。x = 10 nm 器件的电流效率 (CE) 高于 x = 2.5 和 5 nm 的器件，主要是因为 x = 10 nm 时激子形成区的宽度（5.7 nm）大于那些（2.5 和 5 nm） nm)，其中 x = 2.5 和 5 nm。然而，在某个驱动电压下，x = 10 nm 的电流密度比 x = 2.5 和 5 nm 的电流密度降低，因为 ~ 4.3 nm CBP:Ir(ppy) 3 不适应 x = 10 nm 的激子形成起作用运输孔，提高空穴的欧姆损耗，从而提高驱动电压。当 x 从 10 nm 增加到 20 nm 时，激子形成区的宽度从 5.7 nm 增加到 6.8 nm，CE 几乎没有变化，电流密度由于空穴欧姆损耗的增加而降低。目前的研究有助于开发高效、低驱动电压的 PHOLED。