Pushing the frontiers of solar energy

With global energy prices spiking to new highs and temperature records being broken every month, there is an urgent need for clean, renewable technologies to wean us off our dangerous fossil fuel addiction.

Solar cells, or photovoltaics, have long been heralded as the solution, but the real-world efficiency of silicon-based solar cells is generally below 20%, and the production costs are high. However, a type of solar cell that uses a family of materials known as perovskite semiconductors as light absorbers has triggered excitement in the recent years, as the technology has led to the development of perovskite solar cells that are around 26% efficient and they are produced using cheap solution printing methods. Yet while the promise of higher efficiencies and substantially lower production costs has led to lots of research and investment, the commercialisation of the technology continues to face several key challenges. These include the issue of the stability of perovskites.  

To help shed light on the issues affecting perovskite solar cells, Dr Zhou Yuanyuan, Assistant Professor of the Department of Physics at HKBU, and his co-authors from the University of Oxford, City University of Hong Kong and the University of Stuttgart published a review article in Nature Energy, an internationally renowned scientific journal. Titled “Advances and challenges in understanding the microscopic structure–property–performance relationship in perovskite solar cells”, the article synthesizes the overarching knowledge from previous representative studies on perovskites, and it reveals missing information regarding key perovskite microstructures which determine the performance of the solar cells. The authors have also highlighted future directions for research and the commercialisation of the technology.

Pesky perovskites

“We were invited by Nature Energy to write this perspective review on the development and challenges of perovskite solar cells by leveraging a materials-science approach,” says Dr Zhou. “Perovskite is a promising material as it’s cheap, has a higher efficiency, and is easier to produce than traditional solar. You can even print it out. It also has outstanding optoelectronic properties, which are beneficial for the development of novel solar cell applications. Nevertheless, there are fundamental problems that are mostly related to the microscopic structure of these materials.”

In the review, Dr Zhou and his co-authors discussed the morphological characteristics of three key microstructure types encountered in perovskites, which include grain boundaries, intragrain defects and surfaces. The researchers then studied the characteristics of these microstructure types to probe their detrimental, neutral or beneficial effects on perovskites’ optoelectronic properties. The paper also elaborated on the impacts of these microstructures on the degradation modes of perovskites and drew attention to ways that can improve the stability of perovskites.

This paper has filled in the gaps between the previous understanding of perovskites, and it presents overarching fundamental knowledge that may create a profound impact on the technological advancement of the solar energy field.

“One of the most important issues for perovskite solar cells is that they are not as durable as a silicon cell. We need to gain a greater scientific understanding of perovskites in order to achieve a breakthrough. Perovskite microstructures can be very important in terms of final device performance when bringing it to market, so we’ve made a lot of effort to examine and harness the potentials of these microstructures,” says Dr Zhou. “In the review we looked at the perovskite microstructures from a new perspective, and classified them systematically. This helps us identify which aspects of each microstructure have not been fully investigated, and we have also proposed some future research directions for advancing perovskite solar cell development.”

Material world

Dr Zhou trained as a scholar specialising in materials science, and he is enthusiastic about leveraging his expertise to create impacts on the clean energy revolution using transdisciplinary approaches. He received a Bachelor’s degree in Materials Science and Engineering from Xi’an Jiaotong University in China and a PhD in Engineering from Brown University in the USA.

Earlier this year, Dr Zhou received RMB2 million from the National Natural Science Foundation of China’s Excellent Young Scientists Fund (Hong Kong and Macau). With this funding, he will continue to conduct research in materials science with a focus on perovskites, so as to help develop a new generation of photovoltaic and optoelectronic technology. He hopes that the project will not only foster the integration of materials science, semiconductor physics and molecular chemistry, but it will also contribute to the carbon neutrality goal of Hong Kong and the nation by providing technological support. “Perovskite is a very fast-growing field, but there are many things that still haven’t been done, so we have provided a perspective discussion to help bring this new solar technology to the market,” adds Dr Zhou.

For more information about Dr Zhou’s research, please visit https://www.alvinyzhou.com.

Source: DISCOVER HKBU