On the use and influence of electron-blocking interlayers in polymer light-emitting diodes
On the use and influence of electron-blocking interlayers in polymer light-emitting diodes
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DOI：
10.1039/b819200f
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发表时间：
2009-01-01
影响因子：
3.3
通讯作者：
deMello, John C.
中科院分区：
文献类型：
--
作者：
Jin, Rui;Levermore, Peter A.;deMello, John C.
我们报告了一系列聚合物发光二极管的电流-电压-亮度和电调制测量，使用涂覆有聚（3，4-亚乙基二氧噻吩）：聚（苯乙烯磺酸盐）（PEDOT：PSS）的氧化铟锡（ITO）作为阳极，聚（9，9-二辛基芴-alt-N-（4-丁基苯基）-二苯胺）（TFB）作为可选的阳极夹层材料，聚（9，9-二辛基芴-alt-联噻吩）（F8 T2）作为发射层，铝或（铝封端的）钙作为阴极。研究了四种器件结构：ITO/PEDOT：PSS/F8 T2/Al、ITO/PEDOT：PSS/F8 T2/Ca、ITO/PEDOT：PSS/TFB/F8 T2/Al和ITO/PEDOT：PSS/TFB/F8 T2/Ca。与中间层的设备有显着更高的亮度和功率效率比他们的无中间层的对应物的一个事实，我们归因于存在于TFB-F8 T2接口的能量和迁移率的障碍。这些势垒在提高器件效率方面起着两个关键作用：首先，它们使最容易注入的电荷载流子在TFB-F8 T2界面处积累，直到相反载流子类型的有效注入变得有利;其次，它们抑制电子和空穴穿过界面的“渗透”，从而减少漏电流。这两种效应的有益影响对于含中间层的Al器件最为显著，尽管在阴极处对电子注入具有相当大的0.9eV势垒，但该器件在2500 cd·m（-2）的任意参考亮度下表现出令人惊讶的2.4cd·A（-1）和1.1lm·W（-1）的高发光效率和功率效率。与此相比，等效的无中间层器件在25 cd m（-2）时的峰值仅为0.11 cd A（-1）和0.07 lm W-1（在100 cd m（-2）时降至0.058 cd A（-1）和0.025 lm W-1）。含中间层的Ca器件在2500 cd m（-2）下的发光效率和功率效率分别为3.5 cd A（-1）和2.9 lm W-1，而无中间层的等效器件在2500 cd m（-2）下的发光效率和功率效率分别为1.1 cd A（-1）和0.7 lm W-1。
We report current-voltage-luminance and electromodulation measurements on a series of polymer light-emitting diodes, using indium tin oxide (ITO) coated with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) as the anode, poly(9,9-dioctylfluorene-alt-N-(4-butylphenyl)-diphenylamine) (TFB) as an optional anodic interlayer material, poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) as the emissive layer, and either aluminium or (aluminium-capped) calcium as the cathode. Four device structures were investigated: ITO/PEDOT:PSS/F8T2/Al, ITO/PEDOT:PSS/F8T2/Ca, ITO/PEDOT: PSS/TFB/F8T2/Al, and ITO/PEDOT:PSS/TFB/F8T2/Ca. The devices with interlayers had substantially higher luminance and power efficiencies than their interlayer-free counterparts-a fact we attribute to the energy and mobility barriers that exist at the TFB-F8T2 interface. These barriers play two crucial roles in enhancing device efficiency:firstly, they cause the most easily injected charge carrier to accumulate at the TFB-F8T2 interface until efficient injection of the opposite carrier type becomes favourable; and, secondly, they inhibit electron and hole 'seepage' across the interface, thereby reducing leakage currents. The beneficial influence of these two effects is most marked for the interlayer-containing Al device which, in spite of a sizeable 0.9 eV barrier to electron injection at the cathode, exhibited surprisingly high luminous and power efficiencies of 2.4 cd A(-1) and 1.1 lm W-1 at an arbitrary reference luminance of 2500 cd m(-2). This compares with peak values of just 0.11 cd A(-1) and 0.07 lm W-1 at 25 cd m(-2) for the equivalent interlayer-free device (falling to 0.058 cd A(-1) and 0.025 lm W-1 at 100 cd m(-2)). The interlayer-containing Ca device had luminous and power efficiencies of 3.5 cd A(-1) and 2.9 lm W-1 at 2500 cd m(-2) compared to 1.1 cd A(-1) and 0.7 lm W-1 for the equivalent interlayer-free device at 2500 cd m(-2).