Vivian Yam
Philip Wong Wilson Wong Professor in Chemistry and Energy
Chair Professor of Chemistry
Department of Chemistry
The University of Hong Kong
Hong Kong SAR, China
AsianScientist (Nov. 10, 2020) – Think about the last time you observed a beautiful kaleidoscope of city lights from a high vantage point. Not only are these lights prime social media fodder, but they’re also an impressive reminder of the impact of our modern lifestyles. From Hong Kong to Helsinki, nights around the world are getting brighter—but at what cost?
Currently, artificial lights are responsible for nearly one-fifth of global electricity consumption. Of the different kinds of lights, fluorescent lighting is one of the most popular and is seen everywhere from office buildings to grocery stores. However, such lights also contain toxic mercury; if broken, a small amount can be released into the environment. Hence, a safer and more efficient way of producing light is needed.
According to Professor Vivian Yam of the University of Hong Kong, the answer lies the answer lies in photoactive materials like chromophoric and luminescent metal-containing compounds, which possess unique abilities to absorb and emit light. When these compounds are excited, they emit light of different colors when they return to their ground state. By finetuning the excited state of metal-containing compounds, Yam hopes to create strongly luminescent materials for more energy-efficient lighting systems such as organic light-emitting diodes (OLEDs).
Yam’s numerous contributions to photochemistry have garnered her many accolades through the years. In 2001, she made history by becoming the youngest member of the Chinese Academy of Sciences. In this conversation with Asian Scientist Magazine, Yam shares her future research ambitions and advice for younger scientists.
- Energy demand in the Asia Pacific region is projected to almost double by 2030, according to the Asian Development Bank. How can your research help address the surge in demand?
- Your research on photoactive materials is commonly associated with its applications in OLED displays. Can you share with us other unique applications of these materials?
- In 2017 you established a joint laboratory with TCL to explore printable OLED materials. How close are we to commercializing printable OLEDs?
- What new research directions you wish to pursue in the next decade?
- How does effective science communication enhance or benefit your research?
- What advice can you impart to these young aspiring researchers in Asia?
You can imagine how bright a 60-watt tungsten light bulb is. For the same level of brightness, an OLED consumes only eight watts, 13 percent of the power needed by a tungsten light bulb to achieve the same brightness.
When it comes to displays, OLEDs are also more energy-efficient than the typical liquid crystal displays (LCD). After all, LCDs do not emit light and often require backlighting, which in turn, consumes more energy.
An added benefit of creating new photoactive materials is that you can design them to harvest sunlight for photocatalysis. For example, you can separate electrons and holes by shining light to do useful work like reducing protons to produce hydrogen gas in the process. Hydrogen is a promising source of clean, renewable energy.
Photoactive materials have many other useful applications, from energy to health science. For example, a photoactive material that absorbs light near the red end of the solar spectrum can be used to make solar cells that can harvest sunlight.
Some photoactive materials change conformation on light excitation, causing them to absorb light differently. Hence, they can be used to make smart sunglasses that turn dark under the sun and become clear once indoors. We’ve found that similar materials can be used for data storage. Let’s say that the material initially has a yellow color. If you shine a light on it, it turns blue. And then if shine a different wavelength of light, the material will revert to yellow once more. If you consider the material’s yellow form as “0”, and blue as “1”, it can be viewed as a form of binary optical memory for digital data storage.
We can also use photoactive materials for sensing biological molecules. For example, luminescent materials can be used for the real-time monitoring of amyloid formation, which is found in the brains of people with Alzheimer’s disease. We could even use photoactive molecules to encapsulate a drug and stimulate drug release with light. These are just some of the many possibilities offered by photoactive materials.
For printable materials, a major stumbling block is that there are many layers in the OLED device. Furthermore, our choice of materials for these layers is limited. Light is produced in what we call the emissive layer, and we use photoactive materials as a dopant to produce the layer’s desired optical properties. Device performance relies on the compatibility of these materials and so we need a variety of options.
Another difficulty lies in solubility of the photoactive materials and the choice of solvents for solution-processing. You have to dissolve different layers of materials in solvents. But the solvent for materials of one layer should not be able to dissolve another layer, this is known as orthogonal solubility. Otherwise, it will become a blend. Therefore, we need a large library of orthogonally soluble materials.
I want to gain a deeper understanding of the excited state of molecules to create light-emitting materials with better performance. For OLED materials, we are concentrating on gold, but we are now moving towards Earth-abundant metals. Recently, we made an exciting discovery of designing nickel complexes that can emit light at room temperature. If we can make these complexes strongly luminescent, we could create even cheaper OLED materials.
We are also interested in what is called organic resistive memory. We can make molecules that are non-conducting when the applied voltage is lower than a certain threshold voltage, but convert to a higher conductance state once the voltage is higher than the threshold voltage. Similar to optical memory, we call the low-conductance state “0”, and the high-conductance state “1” to create a binary resistive memory for digital data storage. We can further extend the work to ternary resistive memory for higher storage capacity.
From getting research funding to publishing articles, you need to communicate well. Otherwise, no matter how novel or exciting your science is, people won’t understand what you’re talking about.
Nowadays, we do a lot of interdisciplinary collaboration. This means that we need to learn the common language of physicists and biologists, and they need to understand that of a chemist. We should learn to talk in laymen’s terms rather than scientific jargon because even among fellow scientists, not everyone has the same specialty.
It’s also very important to do public outreach. I spend a lot of time teaching undergraduates and doing outreach activities for high school kids. If you cannot communicate, you won’t be able to arouse the interest of the public and disseminate your knowledge to the next generation of academic leaders.
First, be adventurous instead of calculated. Though some research topics may be challenging, you should face the challenge rather than work on something that is safe. Being open to criticism is also important. Whenever I receive comments from reviewers, I try to address every single one as they allow me to think even deeper. Though everyone wants to hear positive comments, criticism enriches your work and thinking, and helps it become more rigorous.
Finally, don’t be arrogant or complacent. Instead of living in the glorious past, look ahead and continue to improve. You have to keep going when working in frontier areas. I always treat myself as a student and I want to learn every day. It’s a lifelong learning process.
This article is from a monthly series called Asia’s Scientific Trailblazers. Click here to read other articles in the series.
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Copyright: Asian Scientist Magazine; Photo: University of Hong Kong.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
