The electroluminescence (EL) of classic and thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) at various vacuum-deposition rates of hole and electron transport layer (HTL and ETL) has been studied. The external quantum efficiency (EQE) measurements showed that the best performance devices were those with a high charge carrier balance inside the emitting layer, which was engineered using hole and electron current manipulation as a result of vacuum-deposition rate control. Changing the vacuum-deposition rate of HTL and ETL leads to a change in the maximum EQE ( $$ {\text{EQE}}_{ {\mathrm{max}} } $$ EQE max ) of the classic and TADF OLEDs without obvious changes in EQE roll-off ratio at high current density. We used a simple analytical model to clarify that the enhanced hole current in HTL at high deposition rates is dominated by high hole mobility attributed to the increased hole hopping rate due to the reduction of the intermolecular separation between horizontally oriented N , N ′-diphenyl- N , N ′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) molecules. The increase in the electron current of tris-(8-hydroxyquinoline) aluminium (Alq 3 ) ETL at low deposition rate was ascribed to high electron injection from cathode into ETL by the fabrication and comparison of J – V characteristic of two electron-only devices with a difference at deposition rate of ETL near cathode interface. Finally, we introduced an OLED with novel gradient and barrier structures for the emitting layer in which high injected charge carriers recombined inside added recombination zone to raise radiative recombination and efficiency of the device. Our results demonstrated that EL efficiency of an OLED can be changed by controlling the vacuum-deposition rate of organic layers.

中文翻译：

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研究在空穴和电子传输层的不同真空沉积速率下有机发光二极管性能的变化

已经研究了经典和热激活延迟荧光 (TADF) 有机发光二极管 (OLED) 在空穴和电子传输层 (HTL 和 ETL) 的各种真空沉积速率下的电致发光 (EL)。外部量子效率 (EQE) 测量表明，性能最佳的器件是那些在发射层内具有高电荷载流子平衡的器件，该器件是通过控制真空沉积速率控制空穴和电子电流而设计的。改变 HTL 和 ETL 的真空沉积速率会导致经典和 TADF OLED 的最大 EQE ( $$ {\text{EQE}}_{ {\mathrm{max}} } $$ EQE max ) 发生变化EQE 滚降比在高电流密度下有明显变化。我们使用一个简单的分析模型来阐明在高沉积速率下 HTL 中增强的空穴电流主要由高空穴迁移率决定，这是由于水平取向的 N , N '-diphenyl- 之间的分子间分离减少导致空穴跳跃率增加。 N , N '-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (α-NPD) 分子。通过制造和比较两种纯电子器件的 J-V 特性，在低沉积速率下三（8-羟基喹啉）铝（Alq 3 ）ETL 的电子电流增加归因于从阴极到 ETL 的高电子注入阴极界面附近的 ETL 沉积速率不同。最后，我们为发光层引入了一种具有新型梯度和势垒结构的 OLED，其中高注入的电荷载流子在添加的复合区域内复合，以提高器件的辐射复合和效率。我们的结果表明，可以通过控制有机层的真空沉积速率来改变 OLED 的 EL 效率。