Small Science: 对话多伦多大学吕正红教授

WILEY旗下新的开放获取(OA)旗舰刊 Small Science近日发表了来自加拿大多伦多大学吕正红教授课题组有关有机电子器件界面工程设计方面的综述论文,全文以(accepted article)正式上线。吕老师是活跃在有机半导体材料与器件领域的国际知名学者之一,长期从事有机半导体器件、器件物理、光电子器件、表面与界面的研究工作。我们特别对话了吕老师,他在介绍了该综述论文作为理解有机电子器件的界面基础的“starting point”之余,也和我们畅谈了他走上科研之路的经历和科研兴趣,并分享了给青年学生的建议。

有机半导体分子具有许多独特的特性,例如可以在任何基材上都能制备出多功能电子器件。其中最具有代表性的器件类型有场效应管,发光二极管以及光伏电池。在这些器件中存在着许多不同材料的界面,例如电极-有机界面和有机-有机界面。界面能级匹配对于载流子的注入和传输起到至关重要的作用,因此影响器件的最终性能。掌握界面能级匹配定律以及载流子传输理论是设计和工程优化有机电子器件的重要基础。

该论文概括总结了近些年来在理解有机界面能级匹配以及载流子传输方面的重要进展。其中着重强调了有机薄膜中分子有序无序性以及分子取向对于界面能级匹配以及载流子传输的影响。有机薄膜中分子的有序无序性直接影响了能级的分布以及载流子在薄膜中的迁移率。分子取向则影响了薄膜的表面静电势,从而影响了其电离能和电子亲和能。这些参数的改变将使得界面能级匹配发生改变,从而影响界面电荷的注入。除此之外,该综述还总结了近些年发展的用于理解界面能级匹配和载流子传输的诸多理论模型,例如基于电化学平衡的通用能级匹配理论,界面载流子注入模型以及主客体材料中的被困电荷热激发跃迁模型等等。这些物理模型可以帮助科研人员预测界面能级匹配以及模拟载流子的传输。最后该综述还提供了实际的器件案例,帮助该领域的科研工作者更好地理解界面能级以及载流子传输对于器件效率的影响。此综述为有机电子器件领域的科研人员在设计以及优化器件结构方面提供了重要的理论基础。相关论文在线发表在Small Science上。(DOI: 10.1002/smsc.202000015)

Lu, Zheng-Hong

Dr. Zheng-Hong Lu is a full professor and a Tier I Canada Research Chair in Organic Optoelectronics at the University of Toronto. He received a PhD degree in engineering physics in 1990 from Ecole Polytechnique of the University of Montreal, Canada. Prior to his current appointment, he was employed by the National Research Council (NRC) as an assistant and then an associate research officer. While at NRC he developed a number of materials and processes for microelectronics and optoelectronics, in particular, light-emitting silicon superlattices, dielectrics for silicon transistors, and surface passivation for solid-state lasers. In 1998, he moved to the University of Toronto to create an Organic Optoelectronics Research Group. His group’s research includes OLED materials and device engineering for flat-panel display and solid-state lighting applications.

SMSC: Could you briefly introduce your research?

LZH: My group has three general research themes: interfaces, thin-film materials and devices. The interface electrical and material integrity are the foundations for integrating multiple categories of materials (metals, ceramics, organics, etc.) in device engineering. For this research theme, we have constructed multi-linked vacuum networks allowing transferring samples in-situ from fabrication chambers/glove boxes to chambers equipped with various characterization tools such photoelectron spectroscopy (XPS/UPS), electrical, optical, etc.. The behavior of electrons and photons in a semiconductor thin-film dictates the performance of devices made of it. We are currently working on developing a variety of semiconductors made of conjugated organic molecules, perovskites, and quantum dots. Regarding devices, we focus on light-emitting diodes, solar cells, and field-effect transistors.  

我们课题组主要的研究兴趣有三个方面:表界面、薄膜材料和器件。在电子器件中,界面(电子界面和材料完整性)是制备并复合多种不同材料(金属,陶瓷,有机物等)的基础。因此,我们构建了多级联的真空网络,可以将样品从制造室/手套箱原位转移到配备有各种表征工具(例如光电子能谱(XPS / UPS),电,光学等)的工作腔中。电子和光子在半导体薄膜中的行为决定了由其制成的器件的性能。我们目前正在开发由共轭有机分子,钙钛矿和量子点制成的各种半导体。在器件方面,我们专注于发光二极管,太阳能电池和场效应晶体管。

SMSC: What got you interested in science in the first place? What is the most attractive thing as a scientist?

LZH: When I was growing up in China in 1960s-1970s, there was not much schooling. I stayed with my parent in a remote mountainous region in Yunnan where my father was sent to build a middle high school. During this time, I spend lots of time wandering in the forest picking wild mushrooms and berries. This perhaps got me interested in nature and natural phenomena.

Being a scientist today, the most attractive and rewarding thing to me is “The Pleasure of Finding Things Out”, which happens to be the autobiography title by Richard P. Feynman.  Being an engineering scientist, I am also attracted to making new and energy-efficient devices.

我在六十年代的中国长大时,那时候国内教育并不发达。我和父母一起住在云南偏远的山区,父亲被派去建立一所中学。在这段时间里,我有很多时间徜徉在森林里采摘野生蘑菇和浆果。这也许使我对自然和自然现象产生了兴趣。时至今日成为科学家,对我而言,最有吸引力和最有意义的是“发现新事物的乐趣”,恰好是理查德·费曼(Richard P. Feynman)自传的书名。 作为一名工程科学家,我也对制造新型节能高效的器件着迷。

SMSC: Who have influenced your career and thinking the most?

LZH: There are so many people, even my graduate students, have helped and influenced me at various stages of my career. One distinct individual is my first group leader Dr. Mike J. Graham of the National Research Council Canada. Mike really mentored me to work with other peers/scientists gracefully and to resolve conflict diplomatically. This has helped my career development smoothly. Thank you, Mike.

有很多人,甚至是我的研究生,在我研究生涯的各个阶段都对我产生了帮助和影响。这其中最特别的是我的第一个课题组长:加拿大国家研究委员会的Mike J. Graham博士。 他指导我与其他同行/科学家一起优雅地工作,并通过“外交”方式解决冲突,这潜移默化地影响了我之后顺利的职业发展。 谢谢你,Mike。

SMSC: Would you like to talk bit more on the Organic Optoelectronics and its future application on display/energy?

LZH: The discovery of organic electroluminescent device can be traced back to 1950s-1960s. One such key paper was reported by National Research Council Canada in a 1965 paper in Physical Review Letters (Vol14/N7). The commercialization wave was started in 1990s by Tokoku Pioneer’s Mr. Ted Tohma, who turned Kodak’s paper of thin-film organic light-emitting diodes (OLED) into area-color displays for car audio. Today, AMOLED display is a key selling feature in high-end smart-phones. LG has successfully made large OLED television sets more and more affordable. With the increasing penetration of new 5G WiFi, AR/VR may soon become the next key enabling technology for multiple industrial sectors. The OLED-on-Si micro-display is the key element in AV/VR industry. Already, Kopin has developed 2.6K OLED micro-display (2560 x 2560 resolution) Flexible and transparent display is another future application. With a new generation of advanced materials, OTI has developed more energy efficient and better transparent displays.I can see the coming of numerous transparent-display-enabled devices.

有机电致发光器件的发现可以追溯到上世纪五六十年代。加拿大国家研究委员会在1965年的《物理评论快报》中报告了关键论文。商业化浪潮是在上世纪90年代由Tokoku Pioneer的Ted Tohma先生发起的,他将柯达的薄膜有机发光二极管(OLED)纸变成了用于汽车音频的彩色显示器。如今,AMOLED显示屏已成为高端智能手机的主要卖点。LG成功地使大型OLED电视机越来越便宜。随着新型5G WiFi的不断普及,AR / VR可能很快成为多个工业领域的下一个关键技术。硅基OLED微型显示器是AV / VR行业的关键要素。Kopin已经开发了2.6K OLED微显示器(2560 x 2560分辨率灵活透明的显示是另一个未来的应用。OTI借助新一代先进材料,开发出了更节能,更透明的显示器。我可以看到更多启用透明显示设备的应用到来。

SMSC: What’s your next project?

LZH: I will continue to research on science and engineering problems related to integration of multiple materials and multiple devices, for the ultimate goal of building a holy device with all components on one-substrate. 

我将继续研究与多种材料和多种设备集成相关的科学和工程问题,以实现将所有组件都集成在一个基板上的终极设备的目标。

SMSC: How do you balance between work and life? What is your hobby?

LZH: Balancing work and life for me is somewhat between two extremes, -work to live and live to work. Hobby could mean a serious time commitment for some people. I just do some leisure activities as my substitutes for “hobbies”. Activities like exploring local food and street while traveling, taking a hike in forest, and playing badminton.

在我看来,平衡工作和生活是在两个极端之间,比如说为了工作而生活和为了工作而生活。业余爱好对某些人来说可能意味着严肃的时间投入。而我只是做一些休闲活动来代替“爱好”,包括在旅行中探索当地美食和街道,在森林里徒步旅行以及打羽毛球。

SMSC: What do you think is the most important characteristic for a researcher? Could you give some advice for researchers starting out in your field?

LZH: Inquisitive mind and strong motivation are the engine and fuel for propelling a researcher to success.

My advice would be to concentrate your energy on understanding fundamental scientific principles without being distracted by “noise”. There are so many papers popping up here and there every day, and so many misinformation from social group chats. These papers and chats could become overwhelming “noise”. As a starting point, read this review paper. It will set you into the right path.

好奇的心态和强烈的自我驱动是推动研究人员走向成功的引擎和力量。我的建议是将精力集中在理解基本的科学原理上,而不会被“噪音”分散注意力。每天到处都有数量繁杂的论文发表,以及来自社交群聊的信息(其中有些可能是错误的)。这些文件和聊天可能会成为压倒性的“噪音”。作为开始这个领域的起点,我想邀请你阅读这篇新发表的评论文章,它会给你一些正确的指导。