量子点发光二极管中载流子注入机理的研究

针对量子点(QDs)发光二极管(QLED)中载流子注 入不平衡的问题,对载流子的注入机理进行了研 究。在隧穿注入和空间电荷限制电流(SCLC)模型的基础上,仿真分析了空穴和电子在QDs 层的注入情况,制备 了QLED的样品。CdSe/CdS作为QDs层,PEDOT:PSS作为空穴注入层(HIL),TPD作为 空穴传输层(HTL),Alq₃作为电子传输层(ETL)。优选的QDs层厚为25nm时,确定了TPD和Alq₃的理论最优厚分别为48nm。研究发现, 当驱动电压低于6.5V时,隧穿注入电流在载流子的传输过 程中起主导作用；高于6.5V时,SCLC在载流子的传输过程中起主导 作用。实验结果表明,当 Alq₃厚为20nm时,器件发出QDs的红光,随着Alq₃厚度的增加, 器件开始出现绿光,实验结果与仿 真结果基本吻合。研究结果对QLED的制备具有理论借鉴意义。

Investigation on the carrier injection mechanism of the quantum dots light emitting diodes

In view of carrier injection unbalance problem of the quantum dots (QDs) ligh t emitting diode (QLED),the mechanism of carrier injection is studied in this paper.Models based on the Folw er-Nordheim (FN) tunneling injection and space-charge limited current (SCLC) conduction are simulated to a nalyze the injection situation of holes and electrons in the QDs layer,and samples of QLED are fabr icated.CdSe/CdS is used as QDs layer,poly(ethylenedioxythiophene):polystyrenesul phonate(PEDOT:PSS)is used as hole injection layer (HIL),N,N/-bis(3-methylphenyl)-N,N/-bis(phenyl)benzidine (TPD) is used as hole transport layer (HTL),and tris-(8-hydroxyquinoline) aluminum (Alq₃) is used as electron transport laye r (ETL).With the thickness of QDs being fixed as 25nm,the optimal thicknesses of TPD and Alq_3are respectively confirmed to be 48nm and 22nm.The simulation results show that when the applied voltage is less than 6.5V,the carrier transport process follows the pattern of the FN tunneling injection,otherwise,it follows the pattern of the SC LC.Experimental results show that the QLED exhibits red light when the Alq_3thickness is 20nm,and the green light b egins to appear with the increase of the Alq_3thickness.The experiment results are basically agree with the simulat ion results.