Yang and his students are continuing their explorations of solar power, leading the rest of us to a brighter future. (photo by Lin Min-hsuan)
Yang Yang is a renowned solar power researcher. Born and raised in Taiwan, he graduated from National Cheng Kung University with a degree in physics before pursuing advanced studies in optoelectronic materials in the US, and is currently a professor at the University of California, Los Angeles (UCLA). His research team has set numerous records for organic solar cell efficiency, and his students have gone on to win positions at famous universities in the US, Japan and elsewhere, and with technology leaders such as Apple, Intel and TSMC. Yang continues to train new generations of top-tier researchers and has been named one of the world’s most influential scientists by the Thomson Reuters media group.
Attitude is everything
When Yang joined the UCLA faculty in 1997, he began his professorial career in a lab not much more than 300 square feet in area and with a research budget of just US$100,000. Both a researcher and an educator, he has always believed that the key traits of successful scientists are personal creativity, perseverance, and the right attitude towards scientific research.
Yang’s research lab has trained more than 100 PhDs and postdoctoral researchers over the last 24 years. Some 40% of these students have gone on to become professors. Another 40% now work for top tech companies, and the remainder have chosen to start their own businesses.
His research group started its research by working on the development of multilayered solar cells that incorporate a variety of materials intended to harvest different parts of the solar spectrum. Two years into their work, they created tandem organic solar cells, which were the first organic solar cells to break the 10% threshold for power conversion efficiency (PCE).
A roll of the dice
Many students who attended leading schools such as National Taiwan University from the 1960s through the 1980s did so in the expectation that they would go on to pursue advanced studies in the United States. Yang, who graduated from National Cheng Kung University in 1982, shared this ambition, leaving Taiwan to enroll in graduate studies at the University of Massachusetts soon after completing his military service. In the US, his professors encouraged their students to ask questions and publish their research, motivating him to transform himself from a middling undergraduate student into a straight-A graduate student.
After getting his PhD, Yang had several offers of jobs that would have paid him around US$45,000 per year, while also providing both stock options and a green card. The National Research Council also selected him as a candidate for a postdoctoral research position. The NRC position didn’t pan out in the end because of a citizenship requirement, but he still felt honored to be considered for one of just 100 post-doc spots at the institution.
The six years Yang spent working as a teaching assistant during graduate school had sparked an interest in a teaching career, but he surprised everyone by choosing instead to take a postdoctoral research position at the University of California, Riverside (UCR). With his wife’s support, he left his comfort zone and moved to California so he could realize his dream of conducting academic research, doing so even though the position paid just US$22,000 per year, or less than half of his private-sector offers, and didn’t include a green card.
Yang and his wife packed up their belongings and spent a week driving the nearly 5000 kilometers from the US East Coast to the West Coast to begin their new California adventure.
A fool for research
A few months after he started working at UCR, California-based Uniax caught his attention with its development of flexible polymer organic LEDs (OLEDs). Intrigued, Yang set up an interview with the company, but it didn’t go as expected. Uniax told him that it had already settled on a researcher from Cambridge, and hoped he wouldn’t be disappointed that it was speaking to him only to meet a US immigration service requirement related to the hiring of foreign technical personnel.
“I’m a never-surrender kind of person,” says Yang. “I do everything I can to put my best foot forward so that people have no grounds to reject me.” Yang’s graduate program was in physics, but he also took courses in electrical engineering and did cross-disciplinary work in chemistry on the way to his PhD in polymer physics. This multidisciplinary background broadened his thinking and set him apart from his peers, with the result that he ultimately got the job with Uniax in spite of the pro-forma nature of the initial interview.
Yang believes that his four years at Uniax were a turning point in his life because they gave him an opportunity to work with world-class people in a variety of fields, including his boss, Alan Heeger, who went on to win the Nobel Prize in chemistry in 2000. Yang developed a broad skillset while working at Uniax, and then joined UCLA’s materials science and engineering faculty in 1997. Here too he faced a fork in the road: he could wait at least ten months to take a tenured position as an associate professor, or immediately start a non-tenured position as an assistant professor. In those days, the field of organic optoelectronics was really coming into its own, and Yang didn’t care much about the status of his position so long as he could seize the moment and continue his research. He therefore accepted the non-tenured position and got down to work.
The following year, Yang and a group of students successfully developed a method for using a modified inkjet printer to print polymer OLEDs. This innovation underlies the ability of companies in the present day to manufacture OLED panels using inkjet printing. The team’s results were reported in the prestigious journal Science, and also earned Yang a National Science Foundation Career Award. People had thought Yang a fool for turning down a tenured position in favor of an earlier start date at UCLA, but Yang had the last laugh when he was promoted to a tenured associate professor position in 1998, and elevated to full professor in 2002.
Inspiring students’ creativity
Yang values his students’ ideas and encourages them to be bold in their thinking. For example, while drinking coffee, a student remembered that caffeine has a boiling point around 300°C, a level far above the operating temperature of solar cells, and wondered if it might increase the stability of solar cell materials. With Yang’s encouragement, the team painted a chemical solution containing caffeine onto conductive glass to form thin-film perovskite solar cells. After thermally aging them for two months, the team found that the caffeine-containing cells retained 86% of their initial PCE. Meanwhile, the control group cells without caffeine retained only 60% of their initial PCE, proving that caffeine really did increase the stability of perovskite solar cells.
When investigating the reason for this result, the team discovered that caffeine molecules help to stabilize the solar cells’ crystal structure by forming “molecular locks” with ions in the cells. But the team’s research work didn’t stop there. They went on to investigate whether molecules such as theophylline (found in tea) and theobromine (found in chocolate) had a similar effect. “They also tested ginseng. It was kind of fun,” says a smiling Yang. In recent years, scientists have been actively seeking breakthroughs aimed at increasing the thermal stability of perovskite solar cells. The team’s research has moved such cells much closer to commercial development.
Yang says, “When we value students’ talents, educate them, and stimulate their potential, they are very likely to excel. When we treat students as labor to be exploited, they only become workhorses.” Yang patiently guides his students towards research they personally find interesting, and then gives them the freedom to choose topics for themselves. When they pick topics they love, they get into their research for the long haul. As a result, scientists trained in his lab can now be found in universities and major corporations all over the world.
Yang has accumulated numerous accolades over the many decades of his research career, including fellowships in the Royal Society of Chemistry and the Materials Research Society. He has led by example, inspiring others to explore the limitless possibilities of optoelectronics and training up new scientists with the knowledge and skills to change the world.
For more pictures, please click 《Training World-Class Talent—Photovoltaics Expert Yang Yang》
