Powering the next generation of solar technology
The breakthrough of Prof. Martin Stolterfoht paves the way for cheaper and more effective solar power solutions.
Researchers from CUHK have made a significant discovery that could extend the operational lifetime of next-generation solar cells and lead to cheaper and more effective solar power technology. The breakthrough addresses a major hurdle in the commercialisation of solar cells made using perovskites rather than traditional silicon.
Solar energy from photovoltaics is one of the most widespread forms of renewable energy. At present, over 95% of solar cells on the market are silicon-based. However, perovskite-based solar cells perform better, are cheaper to produce and have a lower carbon footprint than their silicon counterparts. The problem is that these cells typically last only a few years compared to the decades-long lifespan of silicon cells, a significant barrier to large-scale commercialisation.
Uncovering the primary cause of perovskite degradation loss
Scientists have long sought to understand exactly how perovskite solar cells degrade, with a view to improving their longevity. It was widely believed that degradation is caused by a range of factors such as electronic defects, electrode oxidation, the hybrid nature of perovskites as both electronic and ionic semiconductors, and their tendency to chemically decompose when exposed to moisture and oxygen.
A research team led by Prof. Martin Stolterfoht of the Department of Electronic Engineering has now identified the dominant cause of perovskite solar cells’ instability: the inhibiting effect on the cells’ electric fields caused by the overproduction of mobile ions. This damping of electric fields by mobile electric charge carriers, such as ions or electrons, is known as ‘screening’ in physics.
‘Perovskite semiconductors produce more and more mobile ions when exposed to external stressors, such as illumination,’ Prof. Stolterfoht explains. ‘These ions screen the built-in electric field in the perovskite. This in turn reduces the extraction efficiency of photogenerated electrical charges and, therefore, the current produced by the solar cell. Our research shows that ionic field screening dominates the degradation losses in perovskite solar cells.’
This result was surprising to the researchers, as this phenomenon had not previously been identified as a major cause of degradation loss in perovskite solar cells.
Cross section of the device and illustration of how ion accumulation causes charge extraction losses which leads to increasing performance and degradation losses as more ions are created with time.
A promising development for solar energy
This groundbreaking discovery is crucial for improving the stability of perovskite solar cells to meet industry requirements for a 25-year guaranteed lifetime. Understanding the factors responsible for degradation will enable researchers to develop strategies to enhance cell longevity. For instance, the team’s findings suggest that measuring the ionic properties detected in newly developed devices could be used to accurately predict a cell’s lifespan. This predictive capability could accelerate the development of highly stable perovskite cells without the need for extensive and time-consuming stability tests, as is currently the case.
The research findings, which have been published in the journal Nature Energy, have paved the way for significant advancements in the commercial viability of perovskite solar cells, contributing to a more sustainable future for solar energy technology.
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