Inverting the Handedness of Circularly Polarized Luminescence from Light-Emitting Polymers Using Film Thickness
Inverting the Handedness of Circularly Polarized Luminescence from Light-Emitting Polymers Using Film Thickness
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DOI：
10.1021/acsnano.9b02940
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发表时间：
2019-07-01
期刊：
影响因子：
17.1
通讯作者：
Campbell, Alasdair J.
中科院分区：
文献类型：
--
作者：
Wan, Li;Wade, Jessica;Campbell, Alasdair J.
圆偏振光的发射是许多应用的核心，包括数据存储、光量子计算、生物传感、环境监测和显示技术。从聚合物发光二极管（聚合物OLED; PLED）的活性层诱导（手性）圆偏振（CP）电致发光的新兴方法涉及将非手性聚合物与手性小分子添加剂共混，其中CP光的手性/符号由小分子的绝对立体化学控制。通过深入研究这样一个系统，我们报告了一个有趣的手性性质：能够调整CP光的符号作为活性层厚度的函数的固定对映体的手性添加剂。我们证明，实现这两种高效是可能的（4.0 cd/A）和明亮（8000 cd/m（2））CP-PLED，具有取决于厚度的左手（LH）和右手（RH）光的发射的高度不对称性（薄膜，110 nm：g（EL）= 0.51，厚膜，160 nm：g（EL）=-1.05，术语“厚”和“薄”表示所研究的厚度范围的上限和下限）。我们建议，这是由于本地CP发射分子的手性和CP光放大或反转通过手性介质之间的相互作用。我们链接的形态，光谱和电子表征薄膜和设备的理论研究，努力确定这些意见的基础因素。通过控制有源层厚度和器件结构，本研究提供了深入了解导致CP发光和CP-PLED高性能的机制，以及展示CP光子器件设计的新机会。
The emission of circularly polarized light is central to many applications, including data storage, optical quantum computation, biosensing, environmental monitoring, and display technologies. An emerging method to induce (chiral) circularly polarized (CP) electroluminescence from the active layer of polymer light-emitting diodes (polymer OLEDs; PLEDs) involves blending achiral polymers with chiral small-molecule additives, where the handedness/sign of the CP light is controlled by the absolute stereochemistry of the small molecule. Through the in-depth study of such a system we report an interesting chiroptical property: the ability to tune the sign of CP light as a function of active layer thickness for a fixed enantiomer of the chiral additive. We demonstrate that it is possible to achieve both efficient (4.0 cd/A) and bright (8000 cd/m(2)) CP-PLEDs, with high dissymmetry of emission of both left-handed (LH) and right-handed (RH) light, depending on thickness (thin films, 110 nm: g(EL) = 0.51, thick films, 160 nm: g(EL) = -1.05, with the terms "thick" and "thin" representing the upper and lower limits of the thickness regime studied), for the same additive enantiomer. We propose that this arises due to an interplay between localized CP emission originating from molecular chirality and CP light amplification or inversion through a chiral medium. We link morphological, spectroscopic, and electronic characterization in thin films and devices with theoretical studies in an effort to determine the factors that underpin these observations. Through the control of active layer thickness and device architecture, this study provides insights into the mechanisms that result in CP luminescence and high performance from CP-PLEDs, as well as demonstrating new opportunities in CP photonic device design.