ACAP's pioneering solar PV expert Professor Xiaojing Hao elected to Australian Academy of Science

[This article was originally produced and published by the UNSW Newsroom]

By Stefanie Menezes and Alison Potter

Congratulations to ACAP and UNSW’s Professor Xiaojing Hao who has been elected as a 2025 Fellow of the Australian Academy of Science for her outstanding contributions to the field of photovoltaic technology development. She is among 26 researchers announced as members of the Academy in May, 2025.

Making solar cells cheaper, greener and more efficient

Scientia Professor Xiaojing Hao is driven to squeeze more electricity out of sunlight. Her team at UNSW Engineering leads cutting-edge research to make solar panels more efficient, affordable and sustainable – and translate those results to industry.

Over the past decade, Prof. Hao has emerged as a world leader in her field. She initiated a new line of research in photovoltaics (PV) at UNSW, using the emerging, earth-abundant and non-toxic thin-film material known as ‘sulphide kesterite’ (or copper tin zinc sulphide or CZTS) to develop next-generation solar cells.

Hao has since set many world records for kesterite solar cell efficiency and this year her team (including Ao Wang, Kaiwen Sun, and Jialiang Huang) achieved a 13.2% world record efficiency, which is included in Martin Green’s Solar Cell Efficiency Tables.

Professor Xiaojing Hao's team have lead development of the affordable, non-toxic solar PV thin film material, CZTS. (l-r) Jialiang Huang, Kaiwen Sun, and Scientia Professor Xiaojing Hao and Ao Wang.

This milestone surpasses their previous 11.4% efficiency record and marks a great step towards sustainable photovoltaics (PV).

Key breakthrough published in Nature Energy

One of the major strategies behind these efficiency records is their novel approach of using hydrogen to modulate defects in CZTS, significantly improving device performance. The strategy is also applicable to other PV materials and was published in the highly prestigious journal Nature Energy in January 2025.

Why does CZTS matter?

Prof. Hao’s research is focused on developing affordable, high-efficiency thin film solar cells that can be used on their own or paired with traditional silicon solar cells to form a tandem solar cell. CZTS is an ideal tandem partner for Silicon PV, pushing PV efficiency beyond the single junction limit. 

It’s also stable and made from non-toxic, affordable (earth-abundant) materials, just like silicon, ensuring sustainable and environmentally friendly PV technologies.

Hao said she and her team are committed to further improving CZTS efficiency towards 20%, making it a high-quality material for the future PV market.

“I’m driven by the challenge of pushing the boundaries of photovoltaic technology and delivering meaningful scientific breakthroughs and progress for all,” she said.

“What excites me most about the future of photovoltaics is not just the pace of innovation within the field, but its growing potential to power the future.”

“As costs continue to fall and efficiency rises, we’re seeing PV move far beyond utility-scale power. It’s enabling clean hydrogen production, transforming traditional industries such as mining and transport, and even being integrated into buildings and consumer products. It’s incredibly energising to be part of a field that will fundamentally reshape how we produce, consume, and think about energy across all sectors,” she said.

Prof. Hao said it was an incredible honour to be elected as a Fellow of the Academy of Science. “I feel deeply humbled to be recognised alongside so many scientists whose work I admire. I also truly acknowledge the dedication of my talented students, research fellows, collaborators, and mentors I’ve been fortunate to work with. This recognition belongs just as much to my team, and mentors as to me,” she said.

UNSW Dean of Engineering Professor Julien Epps congratulated Prof. Hao on her fellowship. “This fellowship honours the decades of exceptional and impactful research Scientia Prof. Hao has made in thin-film photovoltaics, including establishing Australia’s leadership in this field,” he said.

“Her work is critically important in improving renewable energy generation to tackle climate change, and I have no doubt she will continue to build on this as a member of the Academy.”