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
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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。Alq_3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Alq_3厚度为30nm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Alq_3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 results show that all the devices exhibit red light and the turn-on voltage rises as the Alq3 thickness increases from 25 nm to 45 nm. When the Alq3 thickness is 30 nm,the current efficiency of the device 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.
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 results show that all the devices exhibit red light and the turn-on voltage rises as the Alq3 thickness increases from 25 nm to 45 nm. When the Alq3 thickness is 30 nm,the current efficiency of the device 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.
引文
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[17]PARKER I D.Carrier tunneling and device characteristics in polymer light-emitting diodes[J].J.Appl.Phys.,1994,75(3):1656-1666.
[18]CARUGE J M,HALPERT J E,BULOVIC'V,et al..Ni O as an inorganic hole-transporting layer in quantum-dot lightemitting devices[J].Nano Lett.,2006,6(12):2991-2994.