結合無機量子點與有機發光材料製作混成式白光二極體之研究

Investigation and fabrication of hybrid inorganic quantum dots and organic material white light emitting diodes

吳辰修(Chen-Hsiu Wu)

指導教授 ： 尤信介

國立交通大學/光電學院/照明與能源光電研究所/碩士(2020年)

摘要

有機發光二極體因其可以做得更輕薄、有彈性、更寬的視場角、更好的能源效率與響應時間，成為受到關注的顯示方法之一。本論文研究分成三個部分，第一部份為討論金屬氧化物摻鎂氧化鋅與三氧化鉬做為載子傳輸層，其摻雜濃度與厚度改變對於元件特性的優化。第二部分使用聚合物SY-PPV做為主體，以它為發光層製作元件，通過改變傳輸層、置入層厚度，製作發光亮度及操作特性最佳之元件。第三部分也使用聚合物SY-PPV做為主體，調整元件結構以期達到製作出白光發光二極體的目的，另外將電洞傳輸層Poly-TPD改以FIrpic摻雜PVK替代之，達成以全有機材料製作而成的白光有機發光二極體。
在倒置結構改變傳輸層的實驗中，製作以摻雜鎂的氧化鋅材料做為電子傳輸層，並與無摻雜之氧化鋅元件做比較，也調整電洞注入層氧化鉬（MoO3）參數。在改變電子傳輸層摻鎂氧化鋅與電洞注入層三氧化鉬實驗中，濃度5%之摻鎂氧化鋅與7.5奈米厚的三氧化鉬搭配有最佳的亮度4,293 cd/m2，為此實驗中最佳的結構組合。摻雜5% 鎂的摻鎂氧化鋅比起10%與15%的元件發光頻譜半高寬值較大，同時也有摻雜濃度越高而使順向電壓（定義為亮度在100 cd/m2時之電壓值）越高的趨勢。
改變各載子傳輸層結構OLED性能研究中，實驗結果顯示，無論增加電子或電洞傳輸層，對電流效率以及亮度皆有提升，順向電壓皆有下降。藉由調整各層厚度參數製作元件，結構ITO/PEDOT：PSS/Poly-TPD（68奈米）/SY-PPV/Alq3（20奈米）/LiF（0.9奈米）/Al，獲得之最佳電流效率為5.7 cd/A、最大亮度121,404 cd/m2、順向電壓4.4伏特（定義為亮度在100 cd/m2時之電壓值）、半高寬值99奈米。
添加藍光無機量子點結合上述有機發光材料製作混成式白光發光二極體，其結構為ITO/PEDOT：PSS/Poly-TPD/SY-PPV（0.1 wt%）/Blue QDs/Alq3/LiF/Al結果順利取得了藍光與黃橘光強度相近的電致發光結果，且色度座標也可以到達白光的範圍（CIE=（0.29,0.31））。最後我們嘗試取代Poly-TPD之電洞傳輸層，改以FIrpic摻雜PVK替代之。並比較所製作之發光元件有無添加藍光量子點操作特性的差異。將Poly-TPD換成FIrpic摻雜PVK後，我們得到藍光強度大幅高於橘光的電激發光結果，但總體亮度下降為原本一成左右。進一步移除藍光量子點後，所製作的元件電激發光量測結果，亮度下降為原本的一半，研判主因為載子不平衡導致。另外，Poly-TPD換成FIrpic摻雜PVK後，順向電壓有稍微的下降，去除藍光量子點後，順向電壓則有明顯的下降。

關鍵字

摻鎂氧化鋅 ； SY-PPV ； 白光有機發光二極體 ； 量子點 ； 倒置結構

並列摘要

Organic light emitting diodes have become one of the most popular display methods because it can be made thinner, more flexible, wider viewing angles, better energy efficiency and response time.This thesis is divided into three parts. The first part is to discuss the magnesium doped zincoxide (MgZnO) and MoO3 as the transport layer, and its doping concentration and thickness change to optimize the device characteristics.The second part uses the polymer SY-PPV as the host and light-emitting layer to make devices.By changing the thickness of the transport layer and the injection layer, the maximum brightness of the structure had been achieved.The third part also uses the polymer SY-PPV as the host, adjusting the structure in order to achieve the purpose of making white light emitting diodes.In addition, the hole transport layer Poly-TPD was replaced with FIrpic doped PVK to achieve white organic light emitting diode made of all organic materials.

In the experiment of changing the carrier transport layer with the inverted structure, a magnesium-doped zinc oxide material was used as the electron transport layer, and compared with the un-doped zinc oxide samples, the MoO3 parameters of the hole injection layer were also adjusted.In the experiment of changing the electron transport layer magnesium-doped zinc oxide and hole transport layer MoO3, the combination of 5% magnesium-doped zinc oxide and 7.5 nm thickness MoO3 have the highest brightness of 4,293 cd / m2, which is the best combination structure in this experiment. Compared with 10% and 15%, MgZnO doped with 5% Mg has a larger full width at half maximum value. At the same time, the higher the doping concentration, the higher the forward voltage (at a brightness of 100 cd / m2).

In the study of the performance of OLEDs that change the carrier transport layer structure.Experiments result shows that either the electron or hole transport layer is added, the current efficiency and brightness are improved, and the forward voltage is reduced.Adjusting the thickness parameters of each layer to make the device, structure ITO/PEDOT:PSS/Poly-TPD(68 nm)/SY-PPV/Alq3(20 nm)/LiF(0.9 nm)/Al, obtain the best current efficiency 5.7 cd/A, maximum brightness of 121,404 cd/m2, forward voltage of 4.4 volts(at a brightness of 100 cd/m2), and a full width at half maximum value of 99 nm are the best characteristics.

Adding inorganic quantum dots combined with the above organic light emitting materials to make the hybrid white light emitting diodes.The structure ITO/PEDOT:PSS/Poly-TPD(15 mg/ml)/SY-PPV(0.1 wt.%)/Blue QDss/Alq3/LiF/Al.As a result, blue light and yellow-orange light with similar intensities were obtained in the electroluminescence results, and the chromaticity coordinates could also reach the white light range(CIE=（(0.29,0.31)).Finally, we tried to replace Poly-TPD as a hole transport layer with FIrpic doped PVK, and compared the characteristics with the device with or without adding quantum dots. After replacing Poly-TPD to FIrpic doped PVK, we get EL results that the blue light intensity is much higher than the orange light, and the brightness drops to about 10%. After the blue light quantum dots were replaced, the brightness decreased by about half.The main reason is that it is caused by carrier imbalance.In addition, the Poly-TPD is replaced with FIrpic doped PVK has a slight decrease in forward voltage. After the blue light quantum dots are removed, the forward voltage drops significantly.

並列關鍵字

MgZnO ； SY-PPV ； WOLED ； Quantum dots ； Inverted structure

參考文獻

[1] Martijn Kuik, Gert-Jan A. H. Wetzelaer, Herman T. Nicolai, N. Irina Craciun, Dago M. De Leeuw, and Paul W. M. Blom, "25th Anniversary Article: Charge Transport and Recombination in Polymer Light-Emitting Diodes," Adv. Mater., vol. 26, iss. 4, pp. 512-531, 2014.

[2] H. Kallmann and M. Pope, "Positive Hole Injection into Organic Crystals," J. Chem. Phys., vol. 32, no. 1, pp. 300-301, 1960.

[3] H. Kallmann and M. Pope, "Bulk Conductivity in Organic Crystals," Nature, vol. 186, Iss. 4718, pp. 31-33, 1960.

[4] M. Pope, H. P. Kallmann,and P. Magnante, "Electroluminescence in Organic Crystals," J. Chem. Phys., vol. 38, no. 8, pp. 2042-2043, 1963.

[5] R. H. Partridge, "Electroluminescence from polyvinylcarbazole films：1. Carbazole cations," Polymer, vol. 24, pp. 733-738, 1983.