Department of Chemistry, The Catholic University of Korea, Bucheon-si, Geyonggi-do 420-753, Korea.
Acc Chem Res. 2012 Apr 17;45(4):544-54. doi: 10.1021/ar2001952. Epub 2011 Nov 15.
π-Conjugated organic molecules represent an attractive platform for the design and fabrication of a wide range of nano- and microstructures for use in organic optoelectronics. The desirable optical and electrical properties of π-conjugated molecules for these applications depend on their primary molecular structure and their intermolecular interactions such as molecular packing or ordering in the condensed states. Because of the difficulty in satisfying these rigorous structural requirements for photoluminescence and charge transport, the development of novel high-performance π-conjugated systems for nano-optoelectronics has remained a challenge. This Account describes our recent discovery of a novel class of self-assembling π-conjugated organic molecules with a built-in molecular elastic twist. These molecules consist of a cyano-substituted stilbenic π-conjugated backbone and various terminal functional groups, and they offer excellent optical, electrical, and self-assembly properties for use in various nano-optoelectronic devices. The characteristic "twist elasticity" behavior of these molecules occurs in response to molecular interactions. These large torsional or conformational changes in the cyanostilbene backbone play an important role in achieving favorable intermolecular interactions that lead to both high photoluminescence and good charge carrier mobility in self-assembled nanostructures. Conventional π-conjugated molecules in the solid state typically show concentration (aggregation) fluorescence quenching. Initially, we describe the unique photoluminescence properties, aggregation-induced enhanced emission (AIEE), of these new cyanostilbene derivatives that elegantly circumvent these problems. These elastic twist π-conjugated backbones serve as versatile scaffolds for the preparation of well-defined patterned nanosized architectures through facile self-assembly processes. We discuss in particular detail the preparation of 1D nanowire structures through programmed self-assembly. This Account describes the importance of utilizing AIEE effects to explore optical device applications, such as organic semiconducting lasers (OSLs), optical memory, and sensors. We demonstrate the rich electronic properties, including the electrical conductivity, field-effect carrier mobility, and electroluminescence of highly crystalline 1D nanowire and coaxial donor-acceptor nanocable structures composed of elastic twist π-conjugated molecules. The electronic properties were measured using various techniques, including current-voltage (I-V), conducting-probe atomic force microscopy (CP-AFM), and space-charge-limited-current (SCLC) measurements. We prepared and characterized several electronic device structures, including organic field-effect transistors (OFETs) and organic light-emitting field-effect transistors (OLETs).
π-共轭有机分子为设计和制造广泛的纳米和微结构提供了一个有吸引力的平台，可用于有机光电。这些应用中π-共轭分子的理想光学和电学性质取决于其主要分子结构及其分子间相互作用，如在凝聚态下的分子堆积或有序化。由于满足这些对于光致发光和电荷输运的严格结构要求具有挑战性，因此开发用于纳米光电的新型高性能π-共轭体系仍然是一个挑战。本账目描述了我们最近发现的一类具有内置分子弹性扭曲的新型自组装π-共轭有机分子。这些分子由氰基取代的二苯乙烯π-共轭主链和各种末端官能团组成，它们在各种纳米光电设备中具有出色的光学、电学和自组装性能。这些分子的特征“扭曲弹性”行为是对分子相互作用的响应。氰基二苯乙烯主链中的这些大扭转或构象变化在实现有利于自组装纳米结构中高光致发光和良好电荷载流子迁移率的有利分子相互作用方面起着重要作用。固态下的常规π-共轭分子通常表现出浓度（聚集）荧光猝灭。最初，我们描述了这些新的氰基二苯乙烯衍生物的独特光致发光性质，即聚集诱导增强发射（AIEE），它们巧妙地规避了这些问题。这些弹性扭曲的π-共轭主链可用作通过简便的自组装过程制备定义良好的图案纳米尺寸结构的通用支架。我们特别详细地讨论了通过程序自组装制备 1D 纳米线结构。本账目描述了利用 AIEE 效应探索光学器件应用的重要性，例如有机半导体激光器（OSL）、光学存储器和传感器。我们展示了丰富的电子性质，包括由弹性扭曲π-共轭分子组成的高度结晶 1D 纳米线和同轴给体-受体纳米电缆结构的电导率、场效应载流子迁移率和电致发光。使用各种技术测量了电子性质，包括电流-电压（I-V）、导电探针原子力显微镜（CP-AFM）和空间电荷限制电流（SCLC）测量。我们制备并表征了几种电子器件结构，包括有机场效应晶体管（OFET）和有机发光场效应晶体管（OLETF）。
