[论文解读] Growth of macroscopic-area single crystal polyacene thin films on arbitrary substrates

Randall L. Headrick, Hua Zhou+8 more|arXiv (Cornell University)|Jul 17, 2011

Organic Electronics and Photovoltaics参考文献 21被引用 3

一句话总结

本文提出一种基于溶剂的沉积方法，可在任意基底上生长宏观尺寸的单晶有机半导体薄膜，包括并五苯及其衍生物6,13-双(三异丙基甲硅烷基乙炔基)并五苯。该技术在并四苯上实现了超过1 cm²的单晶域，在并五苯衍生物上实现了超过2 mm²的单晶域，显著大于传统蒸气沉积或旋涂法产生的微米级晶粒，从而实现高载流子迁移率和更低缺陷，适用于先进有机电子器件。

ABSTRACT

Organic electronic materials have potential applications in a number of low-cost, large area electronic devices such as flat panel displays and inexpensive solar panels. Small molecules in the series Anthracene, Tetracene, Pentacene, are model molecules for organic semiconductor thin films to be used as the active layers in such devices. This has motivated a number of studies of polyacene thin film growth and structure. Although the majority of these studies rely on vapor-deposited films, solvent-based deposition of films with improved properties onto non-crystalline substrates is desired for industrial production of devices. Improved ordering in thin films will have a large impact on their electronic properties, since grain boundaries and other defects are detrimental to carrier mobilities and lifetimes. Thus, a long-standing challenge in this field is to prepare largearea single crystal films on arbitrary substrates. Here we demonstrate a solvent-based method to deposit thin films of organic semiconductors, which is very general. Anthracene thin films with single-crystal domain sizes exceeding 1x1 cm2 can be prepared on various substrates by the technique. Films of 6,13-bis(triisopropylsilylethynyl)pentacene are also demonstrated to have grain sizes larger than 2x2 mm2. In contrast, films produced by conventional means such as vapor deposition or spin coating are polycrystalline with micron-scale grain sizes. The general propensity of these small molecules towards crystalline order in an optimized solvent deposition process shows that there is great potential for thin films with improved properties. Films prepared by these methods will also be useful in exploring the limits of performance in organic thin film devices.

研究动机与目标

• 开发一种可扩展的、基于溶剂的方法，用于在任意基底上生长大面积单晶有机半导体薄膜。
• 克服传统蒸气沉积和旋涂法的局限性，这些方法会产生具有微米级晶界的大块多晶薄膜。
• 在并四苯和并五苯衍生物等小分子有机半导体中实现宏观单晶域（>1 cm²）。
• 通过最小化晶界和缺陷，提升载流子迁移率和器件寿命等电子性能。
• 证明该方法在不同基底和有机半导体材料中的普适性。

提出的方法

• 采用基于溶剂的沉积技术，从溶液中生长薄膜，通过优化溶剂选择和工艺条件以促进晶体有序排列。
• 通过调节溶液浓度、基底表面能和蒸发动力学，实现对单晶域成核和横向生长的可控。
• 该方法应用于并四苯和6,13-双(三异丙基甲硅烷基乙炔基)并五苯，证明其在有机半导体中的广泛适用性。
• 利用光学显微镜、X射线衍射和原子力显微镜对薄膜形貌和结晶性进行表征，以确认其单晶特性。
• 通过调节表面能或使用界面层，实现基底无关性，促进在各种材料上外延式生长。
• 该技术避免使用高真空或热蒸发，可兼容柔性及非晶基底。

实验结果

研究问题

• RQ1 基于溶剂的沉积能否在任意基底上制备出大于1 cm²的单晶有机半导体薄膜？
• RQ2 与蒸气沉积或旋涂法相比，基于溶剂的工艺在晶粒尺寸和结晶度方面有何差异？
• RQ3 使用该方法在并四苯和并五苯衍生物中可实现的最大单晶域尺寸是多少？
• RQ4 该方法是否可推广至不同有机半导体和基底类型？
• RQ5 与多晶薄膜相比，宏观单晶在电子性能方面提升了多少？

主要发现

• 通过基于溶剂的方法，在多种基底上成功生长出尺寸超过1×1 cm²的单晶并四苯薄膜。
• 对于6,13-双(三异丙基甲硅烷基乙炔基)并五苯，实现了超过2×2 mm²的单晶域。
• 该方法的晶粒尺寸显著大于传统蒸气沉积或旋涂法，后者产生具有微米级晶粒的多晶薄膜。
• 该方法在任意基底上均有效，包括非晶态和柔性材料，显示出广泛的基底兼容性。
• 结果表明，小分子有机半导体在优化的溶液处理条件下，具有强烈的形成大尺寸单晶的内在倾向。
• 薄膜表现出高度的结构有序性，表明其在有机场效应晶体管和光伏器件中具有提升载流子迁移率和器件性能的潜力。