电子传输层厚度及阻塞层对量子点发光二极管性能的影响

摘要

针对量子点发光二极管(QLED)中载流子注入不平衡的问题，对空穴和电子在量子点层的注入速率进行了研究。制备了不同电子传输层厚度、结构为 ITO／ PEDOT∶ PSS／ Poly-TPD／ QDs／ Alq3／ Al 的 QLED 样品。Alq3厚度由25 nm 逐步递增至45 nm 时，器件的开启电压升高，器件均发出量子点的红光。当 Alq3厚度为30 nm 时，器件的电流效率最高。此时，空穴和电子在量子点层的注入速率达到相对平衡。为进一步研究器件的发光特性，在 QDs 和 Alq3接触界面嵌入电子阻塞层 TPD。研究发现，当 TPD 的厚度为1 nm 时，器件发出红光；当 TPD 厚度为3 nm 和5 nm 时，器件开始出现绿光。实验结果表明，在选取电子阻塞层时，应选择 LUMO较低的材料且阻塞层的厚度必须很薄。%In view of carrier injection unbalance problem of the quantum dot light emitting diode (QLED), the injection rate of holes and electrons in the quantum dots (QDs) layer was studied. QLED with structure of ITO/ PEDOT∶ PSS / Poly-TPD/ QDs/ Alq3 was fabricated. The experiment re-sults show that all the devices exhibit red light and the turn-on voltage rises as the Alq3 thickness in-creases from 25 nm to 45 nm. When the Alq3 thickness is 30 nm, the current efficiency of the de-vice is high and the injection rate of holes and electrons in the QDs layer reaches a relative balance. Then, the luminescence properties of the devices were further studied through imbedding an electron blocking layer TPD into the QDs/ Alq3 interface. When the TPD thickness is 1 nm, the device still exhibits red light, and green light begins to appear when the TPD thickness is 3 nm and 5 nm. The experiment results show that a thinner thickness and lower LUMO should be chosen for the electron blocking layer.