What’s one thing wearable sensors, LED TVs and solar cells have in common? Aside from being increasingly popular devices in our modern world, these seemingly disparate smart technologies are all enabled by polymer and organic electronics—a vibrant field that studies the applications of soft, flexible, and conductive organic materials for electronic devices.
In recent years, organic optoelectronics based on the interplay between light and electrical energy, like organic light-emitting diodes (LEDs) and perovskite solar cells, have grown in prominence as electronic devices look to interact with the world around them. From X-rays to visible light, these devices can sense and control waves across the electromagnetic spectrum to great effect. But while organic optoelectronics-based gadgets are already commercially available, key challenges remain.
Consider the trade-off between stability and efficiency. Though optoelectronic devices made from organic materials promise to be more energy-efficient, these same materials can chemically degrade under light, resulting in short lifespans. At A*STAR’s Institute of Materials Science & Engineering (IMRE), scientists like Junior Group Leader Le Yang from the PRinted Organic Flexible Electronics & SenSors (PROFESS) group are seeking to achieve the elusive goal of both stability and efficiency in a single system.
In this interview with A*STAR Research, Yang talks about her initial foray into the exciting world of organic and polymer electronics as well as optoelectronics. She also discusses her efforts to take these devices to new heights—and new applications.
1. Given your initial training in chemistry, what sparked your later interest in optoelectronics?
In the early days of my learning journey, I had always been interested in the more ‘biology’ side of science. This interest led me to want to pursue biological and medicinal chemistry during my undergraduate chemistry studies at Imperial College London.
However, I increasingly realized my dislike towards organic synthesis, a subject I thought I liked! Luckily, a summer project in polymers applicable to battery applications and a final year project on semiconductor polymers sparked my interest in optoelectronics and energy-related research.
These experiences opened my eyes to an exciting multidisciplinary field that I had never considered before. This led to a one-year, pre-PhD attachment at IMRE, working on printable electronics and organic solar cells.
My interest blossomed even further during my postgraduate years at the University of Cambridge, where I read Physics in organic optoelectronics. It’s hard to explain exactly why I was so attracted to this research field, but understanding materials and devices and their role in fabricating high-efficiency optoelectronics was certainly a key factor.
Today, I find building better devices, enhancing their performance and watching their performance improve to be an addictive experience. Knowing that my research is practical and use-inspired is also very compelling to me.
2. Among your research projects, which are you most proud of? Why?
Most of my completed work involves fabricating electronic devices like solar cells, LEDs and now sensors and other functional structures.
I felt great pride when our team discovered a new emission pathway in a class of new emitters. In fact, I built solution-processed organic LEDs in the lab that broke the world efficiency record.
I remember when I achieved that unprecedented efficiency. I was so shocked that I dropped my phone the moment I saw the measurement. That drop smashed my phone screen and I had to fork out S$200 to fix it. True story, but a happy one nonetheless!
Apart from improving device efficiency, this discovery opens new routes to achieving printable high-efficiency organic LEDs for display tech.
3. What fundamental questions do you hope to address with your research?
Currently, with IMRE’s support, I am embarking on two research fronts with the first being developing wearable electronics and sensors.
I’ve been blessed with the opportunity to be involved in the Cyber Physiochemical Interfaces (CPI) program, led by Xiaodong Chen and supported by a valuable and endearing team at IMRE. We aim to bring integrated solutions to non-invasive and real-time wearable sweat sensing, applicable for healthtech, medtech, forensics and more.
This medtech endeavor has been new to me. Our team (Xinting Zheng, Yong Yu, Yuxin Liu, Changyun Jiang and Wei Peng Goh) came together because of this project, and I am humbled and honored to know and work alongside them.
My second research area aims to use organic materials in sustainably building functional structures and optoelectronic devices. We aim to study and fully utilize the photophysics of organic optoelectronic materials in constructing energy-efficient or energy-harvesting devices.
A fundamental challenge in organic luminescence is the lack of versatility in manipulating high-energy light. Despite this, high-energy light is critical in many applications from optogenetics to anti-counterfeiting. Yet, it could also be detrimental to our eyes and skin, our circadian rhythm and even to solar cells.
Therefore, converting to other colors in an energyconserving way would be beneficial. These studies can serve applications such as display tech, agritech, solar tech, sensing and more. We also hope to address some of the biosensor challenges mentioned above with novel optoelectronic strategies.
4. Where else can research into cyber–physiochemical interfaces be applied?
We hope that the capabilities we have built through the CPI programme can form platform technology for sensing. Currently, we are mainly targeting on-skin medtech and healthtech in the move towards digital healthcare, cloud-based and personalized medtech, and lifestyle monitoring. We are also gradually exploring sensing for forensic applications and other areas such as food or the environment.
5. How can the optoelectronic devices you develop improve display and solar energy technologies?
We can achieve this by working with organic materials that are light, flexible and sometimes stretchable. Furthermore, some organic molecules are more readily biodegradable.
Our goal is to build optoelectronic devices that are long-lasting, more stable and energy-efficient, while achieving high performance at the same time—be it for display, lighting or solar energy harvesting. One challenge working with organic optoelectronic devices is achieving both stability and efficiency simultaneously in one system. We certainly hope to design strategies to overcome that.
We are also designing and developing passive structures that do not need additional energy input for functional applications. For instance, we are excited about potential use cases for plant growth. Stay tuned!
