Induction of circularly polarized electroluminescence from an achiral light-emitting polymer via a chiral small-molecule dopant.
Induction of circularly polarized electroluminescence from an achiral light-emitting polymer via a chiral small-molecule dopant.
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DOI：
10.1002/adma.201204961
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发表时间：
2013-05-14
影响因子：
29.4
通讯作者：
Fuchter, Matthew J.
中科院分区：
文献类型：
--
作者：
Yang, Ying;da Costa, Rosenildo Correa;Smilgies, Detlef-M.;Campbell, Alasdair J.;Fuchter, Matthew J.
关键词：
有机发光二极管（oled）是一种利用在两个电极之间夹有发光电致发光有机半导体（OSC）薄膜的器件。采用聚合物作为OSC是一种非常有吸引力的方法，因为它们易于溶液处理。这使得使用印刷技术制造低成本、大面积设备成为可能。圆偏振光是当前和未来显示和光子技术的核心，包括高效LCD背光，光量子信息处理和通信，[2,3]和光学自旋电子学因此，人们对构造cp发光器件非常感兴趣。虽然在聚合物LED （PLED）器件中使用宽带反射偏振器作为无源元件是设计CP光输出的一种方法，但这会导致相对复杂和厚实的器件架构，需要额外的液晶电池从传统的PLED直接产生CP光在简单、紧凑、能源效率和产品成本方面要有利得多，因此对它们的发展有很大的兴趣。迄今为止，制造直接cp发光led的主要策略是将悬垂的手性侧链附着在非手性共轭聚合物骨架上。这种体系的圆二色性或cp发射程度由不对称因子（g因子，其中| g|≤2）来定义，其中gabs描述圆二色性，gPL描述cp光致发光，gEL描述cp电致发光。虽然使用这种方法的早期成功尝试，例如手性取代的聚（对苯基乙烯）（PPV），只获得了10−3的凝胶，但大量的合成和设备优化工作导致聚合物的凝胶高达0.35（见支持信息，表S1的比较数据）。随后的分析确定了手性侧链的作用，使聚合物排列成手性排列。[7,8]一种非常简单且可高度翻译的替代方法应该是使用手性小分子掺杂剂与传统的非手性发光聚合物（LEP）混合来诱导这种效应。这将避免定制聚合物合成的需要，并可能允许使用广泛的设备优化共聚物，在整个视觉光谱中发射。然而，虽然有少数报道使用相对较大的手性分子结构，如多糖、[9]联芳基化合物、[10]或手性溶剂混合物[11]来诱导共轭聚合物的cp -光致发光（CP-PL），但这些方法或掺杂剂在转化为固态方面有很大的局限性。因此，直接CP-EL发射器件的制造以前还没有被证明用这种方法。此外，从这些研究中观察到的CP-PL水平非常低（gPL= 10−2至10−3，见支持信息，表S1），因此远不能与具有手性侧链的聚合物竞争。螺旋烯本质上是螺旋的（因此是手性的）共轭分子，基于融合的碳环或杂环[12]的螺旋（例如图1a）。它们可以分为右手对映体和左手对映体，众所周知，右手对映体具有强旋光性，如高旋光能力和强圆二色性。[12,13]本文涉及我们的初步研究，以探讨螺旋蛋白是否可以作为手性掺杂剂，并将其螺旋形状的性质赋予传统的…
Organic light-emitting diodes (OLEDs) are devices that utilize an emissive electroluminescent organic semiconductor (OSC) thin film sandwiched between two electrodes. Employing polymers as the OSC is a highly attractive approach due to their easy solution processibility. This results in low cost, large area device fabrication possibilities using printing techniques. Circularly polarized (CP) light is central to a large range of current and future display and photonic technologies, including highly efficient LCD backlights,[1] optical quantum information processing and communication,[2, 3] and optical spintronics.[4] There is therefore high interest in constructing CP-light-emitting devices. Whilst the use of wide-band reflective polarizers as passive components in polymer LED (PLED) devices is one means to engineer a CP light output, this results in a relatively complex and thick device architecture, requiring an additional liquid-crystal cell.[5] The direct generation of CP light from a conventional PLED would be far more favorable in terms of simplicity, compactness, energy efficiency and product cost, and thus there has been significant interest in their development. The principle strategy to date to fabricate direct CP-lightemitting PLEDs has been the attachment of pendent chiral sidechains onto achiral conjugated polymer backbones. The degree of circular dichroism or CP-emission obtained from such systems is defined by the dissymmetry factor (g factor, where| g|≤ 2), with gabs describing circular dichroism, gPL describing CP-photoluminescence and gEL describing CP-electroluminescence. Whilst early successful attempts at using this approach, for example with a chiral-substituted poly (p-phenylene vinylene)(PPV), only obtained gEL in the region of 10− 3,[6] considerable synthesis and device optimization effort has resulted in polymers with gEL up to 0.35 (see Supporting Information, Table S1 for comparative data). Subsequent analysis has established the role of the chiral pendent side chain, in aligning the polymer into a chiral arrangement.[7, 8] An elegantly simple and highly translatable alternative approach should be the use of a chiral small-molecule dopant to induce this effect by blending it with a conventional achiral light-emitting polymer (LEP). This would avoid the need for bespoke polymer synthesis and could potentially allow the use of a wide range of device-optimized copolymers emitting across the full visual spectrum. However, whilst a small number of reports have emerged on using relatively large chiral molecular architectures such as polysaccharides,[9] biaryl compounds,[10] or chiral solvent mixtures [11] in order to induce CP-photoluminesence (CP-PL) from conjugated polymers, these approaches or dopants have significant limitations for translation into the solid state. Therefore the fabrication of direct CP-EL emitting devices has not been previously demonstrated by this method. Furthermore, the level of CP-PL observed from these studies was only very low (gPL= 10− 2 to 10− 3, see Supporting Information, Table S1), thus being far from competitive with the polymers bearing chiral side-chains. Helicenes are intrinsically helical (and therefore chiral) conjugated molecules based on a spiral of fused carbocyclic or heterocyclic rings [12](for example Figure 1a). They can be separated into their right-handed and left-handed enantiomeric forms, which are well known to exhibit strong chiroptical properties, such as high optical rotatory power and strong circular dichroism.[12, 13] This paper concerns our preliminary studies to investigate whether helicenes would act as a chiral dopant and confer their helical shape properties to a conventional …
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