Thickness Estimation Method for Every Functional Layer of QLEDs

为改善量子点发光二极管器件载流子注入平衡，提出一种量子点发光二极管各功能层厚度的确 定方法．首先选定量子点发光层厚度，基于隧穿模型进行仿真分析确定电子传输层厚度；然 后 采 用 空 间 电荷限制电流模型进行仿真分析确定空穴传输层厚度．采 用 ＣｄＳｅ／ＺｎＳ 量子点作为发光层、ｐｏｌｙ－ＴＰＤ 作为空穴传输层、Ａｌｑ３ 作为电子传输层，按照该方法仿真分析得到各功能层厚度进行旋涂－蒸 镀 法 实 物器件制备．对比实验结果表明：当ｐｏｌｙ－ＴＰＤ、ＱＤｓ及 Ａｌｑ３ 厚度分别为４５ｎｍ、２５ｎｍ 及３５ｎｍ 时，获 得了较高的发光效率及色纯度，器件性能最好．该方法确定的各功能层厚度有助于减少载流子在发光界 面积累，获得载流子的注入平衡，从而改善 ＱＬＥＤｓ发光性能． 关键词：量子点发光二极管；载流子注入平衡；空穴传输层；发 光 层；电 子 传 输 层；隧 穿 模 型；空 间 电 荷 限 制电流模型

To balance the carrier injection in Quantum Dot Light Emitting Diode (QLEDs), a method to determine the thickness of each functional layer was proposed. The thickness of EL was set firstly, the thickness of Electron Transport Layer (ETL) was determined through tunneling model. On this basis, the thickness of Hole Injection Layer (HTL) was determined at last using space charge limited current model. Devices using red light CdSe/ZnS quantum dot was used as the Light-Emitting Layer (EL), poly-TPD as the HTL, Alq3 as the ETL were fabricated through spin-coating and vacuum evaporation with the thickness of each layer obtained from the simulation results. Experiment results show that compared with other devices, the device with a 45 nm thickness of poly-TPD, 25 nm QDs and 35 nm Alq3 has a higher luminous efficiency and color purity. QLEDs with the thickness of each layer chosen according to the method proposed have a more balanced carrier injection which is advantageous in improving device performance.