This Engineer’s Solar Panels Are Breaking Efficiency Records

When Yifeng Chen was a teenager in Shantou, China, in the early 2000s, he saw a TV program that amazed him. The show highlighted rooftop solar panels in Germany, explaining that the panels generated electricity to power the buildings and even earned the owners money by letting them sell extra energy back to the electricity company.

Yifeng Chen

Employer

Trina Solar

Title

Assistant vice president of technology

Member Grade

Member

Alma Maters

Sun Yat-sen University, in Guangzhou, China, and Leibniz University Hannover, in Germany

An incredulous Chen marveled at not only the technology but also the economics. A power authority would pay its customers?

It sounded like magic: useful and valuable electricity extracted from simple sunlight. The wonder of it all has fueled his dreams ever since.

In 2013 Chen earned a Ph.D. in photovoltaic sciences and technologies, and today he's assistant vice president of technology at China's Trina Solar, a Changzhou-based company that is one of the largest PV manufacturers in the world. He leads the company's R&D group, whose efforts have set more than two dozen world records for solar power efficiency and output.

For Chen's contributions to the science and technology of photovoltaic energy conversion, the IEEE member received the 2023 IEEE Stuart R. Wenham Young Professional Award from the IEEE Electron Devices Society.

I was quite surprised and so grateful" to receive the Wenham Award, Chen says. It's a very high-level recognition, and there are so many deserving experts from around the world."

Trina Solar's push for more efficient hardware

Today's commercial solar panels typically achieve about 20 percent efficiency: They can turn one-fifth of captured sunlight into electricity. Chen's group is trying to make the panels more efficient.

The group is focusing on optimizing solar cell designs, including the passivated emitter and rear cell (PERC), which is the industry standard for commodity solar panels.

Invented in 1983, PERCs are used today in nearly 90 percent of solar panels on the market. They incorporate coatings on the front and back to capture sunlight more effectively and to avoid losing energy, both at the surfaces and as the sunlight travels through the cell. The coatings, known as passivation layers, are made from materials such as silicon nitride, silicon dioxide, and aluminum oxide. The layers keep negatively charged free electrons and positively charged electron holes apart, preventing them from combining at the surface of the solar cell and wasting energy.

Chen and his team have developed several ways to boost the performance of PERC panels, hitting a record of 24.5 percent efficiency in 2022. One of the technologies is a multilayer antireflective coating that helps solar panels trap more light. They also created extremely fine metallization fingers-narrow lines on solar cells' surfaces-to collect and transport the electric current and help capture more sunlight. And they developed an advanced method for laying the strips of conductive metal that run across the solar cell, known as bus bars.

Experts predict the maximum efficiency of PERC technology will be reached soon, topping out at about 25 percent.

IEEE Member Yifeng Chen displays an i-TOPCon solar module, which has a production efficiency of more than 23 percent and a power output of up to 720 watts.Trina Solar

So the question is: How do we get solar cells even more efficient?" Chen says.

During the past few years he and his group have been working on tunnel oxide passivated contact (TOPCon) technology. A TOPCon cell uses a thin layer of tunneling oxide" insulating material-typically silicon dioxide-which is applied to the solar cell's surface. Similar to the passivation layers on PERC cells, the tunnel oxide stops free electrons and electron holes from combining and wasting energy.

In 2022 Trina created a TOPCon-type panel with a record 25.5 percent efficiency, and two months ago the company announced it had achieved a record 740.6 watts for a mass-produced TOPCon solar module. The latter was the 26th record Trina set for solar power-related efficiencies and outputs.

To achieve that record-breaking performance for their TOPCon panels, Chen and his team optimized the company's manufacturing processes including laser-induced firing, in which a laser heats part of the solar cell and creates bonds between the metal contacts and the silicon wafer. The resulting connections are stronger and better aligned, enhancing efficiency.

We're trying to keep improving things to trap just a little bit more sunlight," Chen says. Gaining 1 or 2 percent more efficiency is huge. These may sound like very tiny increases, but at scale these small improvements create a lot of value in terms of economics, sustainability, and value to society."

As the efficiency of solar cells rises and prices drop, Chen says, he expects solar power to continue to grow around the world. China currently leads the world in installed solar power capacity, accounting for about 40 percent of global capacity. The United States is a distant second, with 12 percent, according to a 2023 Rystad Energy report. The report predicts that China's 500 gigawatts of solar capacity in 2023 is likely to exceed 1 terawatt by 2026.

I'm inspired by using science to create something useful for human beings, and then driven by the pursuit for excellence," Chen says. We can always learn something new to make that change, improve that piece of technology, and get just that little bit better."

Trained by solar-power pioneers

Chen attended Sun Yat-sen University in Guangzhou, China, earning a bachelor's degree in optics sciences and technologies in 2008. He stayed on to pursue a Ph.D. in photovoltaics sciences and technologies. His research was on high-efficiency solar cells made from wafer-based crystalline silicon. His adviser was Hui Shen, a leading PV professor and founder of the university's Institute for Solar Energy Systems. Chen calls him the first of three very important figures in my scientific career."

In 2011 Chen spent a year as a Ph.D. student at Leibniz University Hannover, in Germany. There he studied under Pietro P. Altermatt, the second influential figure in his career.

Altermatt-a prominent silicon solar-cell expert who would later become principal scientist at Trina-advised Chen on his computational techniques for modeling and analyzing the behavior of 2D and 3D solar cells. The models play a key role in designing solar cells to optimize their output.

Gaining 1 or 2 percent more efficiency is huge. These may sound like very tiny increases, but at scale, these small improvements create a lot of value in terms of economics, sustainability, and value to society."

Dr. Altermatt changed how I look at things," Chen says. In Germany, they really focus on device physics."

After completing his Ph.D., Chen became a technical assistant at Trina, where he met the third highly influential person in his career: Pierre Verlinden, a pioneering photovoltaic researcher who was the company's chief scientist.

At Trina, Chen quickly ascended through R&D roles. He has been the company's assistant vice president of technology since 2023.

IEEE's treasure" trove of research

Chen joined IEEE as a student because he wanted to attend the IEEE Photovoltaic Specialists Conference, the longest-running event dedicated to photovoltaics, solar cells, and solar power.

The membership was particularly beneficial during his Ph.D. studies, he says, because he used the IEEE Xplore Digital Library to access archival papers.

My work has certainly been inspired by papers I found via IEEE," Chen says. Plus, you end up clicking around and reading other work that isn't related to your field but is so interesting.

The publication repository is a treasure. It's eye-opening to see what's going on inside and outside of your industry, with new discoveries happening all the time."