Solution-Processed White Phosphorescent Tandem Organic Light-Emitting Devices
Solution-Processed White Phosphorescent Tandem Organic Light-Emitting Devices
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DOI：
10.1002/adma.201501866
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发表时间：
2015-08-26
影响因子：
29.4
通讯作者：
Kido, Junji
中科院分区：
文献类型：
--
作者：
Chiba, Takayuki;Pu, Yong-Jin;Kido, Junji
DOI：10.1002/adma.完全基于溶液制造串联OLED的方法在很大程度上取决于MoO 3和薄金属的替代溶液可加工材料的可用性。[27由CGL和EIL材料组成的互连层必须不仅由溶液形成而不溶解底层，而且不溶于随后的上层的涂覆溶剂。脂族胺聚合物如聚乙烯亚胺（PEI）和聚乙烯亚胺乙氧基化（PEIE）的单层，以及ZnO纳米颗粒/PEI或PEIE双层已被用作有机光致发光（OPV）[29-32]或OLED中EIL [29，33-35]; PEI或PEIE层由于界面偶极效应容易降低ZnO和电极如ITO的功函数。[29]另一方面，各种金属氧化物，如MoO 3，V2 O 5，WO 3和NiOx已被研究作为溶液处理的OLED的空穴注入层（HIL）和OPV的空穴收集层。[36最近，Höfle等人成功地实现了溶液处理的串联OLED的制造，其中互连层包含用PEI和WO 3改性的ZnO。[38]Pu等人以磷钼酸水合物（MoO 3）12·H3 po 4·（H2o）x（PMA）为电子受体材料，采用溶液法制备了规则结构的串联有机发光器件。[39]在这两篇关于溶液处理的串联OLED的先前报道中，由于在有机溶剂中的溶解度比小分子材料低得多，LEU限于荧光π-共轭聚合物如Super Yellow或聚（9，9-二辛基芴-alt-苯并噻二唑）（F8 BT）的应用。为了进一步提高器件效率，使用磷光发光材料是必要的，因为它们具有高的内量子效率。[40最近，Aizawa等人报道了具有小分子材料的溶液处理的磷光OLED的效率比具有聚合物材料的溶液处理的磷光OLED的效率高得多。[42]在溶液处理串联有机发光二极管的发展中，小分子和磷光发光材料在器件中的应用将成为一个越来越重要的挑战。在本文中，我们描述了溶液处理的串联OLED，包括两个磷光LEU与小分子发光掺杂剂，小分子主体材料，和作为粘合剂的聚合物材料，提高不溶性的LEU膜。ZnO纳米颗粒/PEIE双层用作每个LEU中的EIL，并且聚（3，4-乙撑二氧噻吩）：聚（苯乙烯磺酸盐）（PEDOT：PSS）用作互连导电层。ZnO纳米颗粒与PSS中的酸性官能团之间的反应不允许ZnO纳米颗粒均匀地旋涂到原始酸性PEDOT：PSS上。
DOI: 10.1002/adma. 201501866 of a completely solution-based fabrication of tandem-OLEDs is largely dependent on the availability of alternate solution-processable materials for MoO 3 and thin metals.[27, 28] The interconnecting layer consisting of CGL and EIL materials have to be not only formed from solution without dissolving bottom layer but also insoluble to coating solvents for subsequent upper layers. Additionally, low annealing temperature is required for the interconnecting layer to suppress thermal influence to the bottom LEUs.The monolayers of aliphatic amine polymers such as polyethyleneimine (PEI) and polyethlyeneimine-ethoxylated (PEIE), and ZnO nanoparticles/PEI or PEIE bilayers have been used as solution-processable electron-collection layers in organic photovoltaics (OPVs)[29–32] or EILs in OLEDs [29, 33–35]; PEI or PEIE layers readily reduce the work function of ZnO and electrodes such as ITO as a result of interfacial dipole effect.[29] On the other hand, various metal oxides, eg, MoO 3, V2o 5, WO 3, and NiO x have been studied as solution-processed hole-injection layers (HILs) of OLEDs and hole-collection layers of OPVs.[36, 37] Recently, Höfle et al. successfully achieved fabrication of solution-processed tandem-OLEDs with the interconnecting layer comprising ZnO modified with PEI and WO 3.[38] Pu et al. fabricated regular structure of tandem-OLEDs by solution process with phosphomolybdicacid hydrate (MoO 3) 12· H3po 4·(H2o) x (PMA) as the electron-accepting material for CGL.[39] In these two previous reports on solution-processed tandem-OLEDs, LEUs are limited to application of fluorescent π-conjugated polymers such as Super Yellow or poly (9, 9-dioctylfluorene-alt-benzothiadiazole)(F8BT) due to much lower solubility in organic solvents than that of small molecular materials. In order to further improve device efficiency, using phosphorescent emitting materials are necessary due to their high internal quantum efficiency.[40, 41] Recently, Aizawa et al. reported much higher efficiency of solution-processed phosphorescent OLEDs with small molecule materials than that with polymer materials.[42] In the development of solution-processed tandem-OLEDs, application of small molecule and phosphorescent emitting materials into the devices would become an ever more important challenge. In this paper, we describe solution-processed tandem-OLEDs comprising two phosphorescent LEUs with small molecule emitting dopants, small molecule host materials, and a polymer material as a binder improving insolubility of the LEU films. The ZnO nanoparticle/PEIE bilayer serves as the EIL in each LEU, and poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate)(PEDOT: PSS) is used as the interconnecting conductive layer. The reaction between ZnO nanoparticles and the acidic functionalities in PSS does not allow for ZnO nanoparticles to be uniformly spin coated onto the pristine acidic PEDOT: PSS