Engineers at the University of New South Wales (UNSW) have reportedly achieved a world record for the efficiency of kesterite solar cells, a material considered key to future photovoltaic technologies.
The UNSW team, led by Scientia Professor Xiaojing Hao, has achieved a photovoltaic efficiency of 13.2 per cent for high bandgap kesterite solar cells, enhanced with hydrogen.
This milestone marks an improvement for kesterite, a naturally occurring mineral that can also be synthesised at low cost using copper, zinc, tin, and sulfur—materials that are abundant and non-toxic.
The achievement builds on six years of research aimed at overcoming the challenges posed by kesterite’s efficiency, the university stated in a news release.
Researchers said previous efforts had been stymied by the defects created during the production of the material.
By heat-treating kesterite in a hydrogen-containing atmosphere, the UNSW team, including Dr Kaiwen Sun and Dr Jialiang Huang, has found a way to reduce the impact of these defects, improving the material’s ability to convert sunlight into electricity. This process, known as passivation, helps to enhance the photovoltaic efficiency of the material.
The breakthrough comes after years of stagnation for kesterite, with its efficiency remaining at 11 per cent for over six years.
Professor Hao explained that the next step is to further reduce defects and increase the material’s efficiency, with the goal of reaching 15 per cent within the next year and commercializing the technology by 2030.
The findings, which were published in Nature Energy, represent a major step forward in the search for an efficient and cost-effective alternative to silicon-based solar cells.
Professor Hao’s work on kesterite is part of a broader effort to develop tandem solar cells, which combine two or more solar cells to capture more of the solar spectrum and increase efficiency.
Kesterite’s potential for use in tandem cells is particularly promising due to its environmental friendliness, low cost, and long-term performance.
“But we know that this is a good material. When we consider the requirements from the bottom up, we know that we need something that is widely abundant, that is environmentally friendly, that has good optoelectronic properties and can last a long time – and CZTS fits the bill,” she said.
While perovskite, another potential material for tandem solar cells, offers higher efficiency, it suffers from stability issues and the presence of toxic components.
Professor Hao cautioned that while perovskite-based cells may initially perform well, their limited lifespan makes them unsuitable for long-term use. In contrast, kesterite presents a sustainable option with the potential for even greater efficiency.
“It can take a long time to solve those problems, whereas with CZTS if we can get it to 20% efficiency then I think it will really take off because there are no other limitations since it meets all the criteria for the type of material we want to be using,” she said.
