The National Renewable Energy Laboratory (NREL) in the US has developed accelerated indoor stability testing protocols that it believes can help predict the actual functioning of perovskite solar cells in real conditions, thus nudging the technology towards commercialization.
Their rationale is that the cells need to be tested under harsh conditions with variable combinations of changing stress factors to be able to judge their stability. Right now, most researchers prefer to conduct the tests indoors with few fixed stressing conditions.
"We must understand how well perovskite solar cells will perform outdoors, under real conditions, to move this technology closer to commercialization," said a Senior Scientist in the Chemistry and Nanoscience Center at NREL, Kai Zhu. "That's why we identified accelerated testing protocols that can be conducted in the laboratory to reveal how these cells would function after six months in operation outside."
For its research to show indoor accelerated stability tests can predict 6-month outdoor aging tests, the NREL team uses metal halide perovskite cells with an efficiency of up to 25.5%.
These were subjected to thermal cycling under temperatures fluctuating between -40º C and 85º C. After 1,000 cycles, the cells showed an average degradation of about 5%. These retained more than 93% of their maximum efficiency after about 5,030 hours of continuous operation.
According to the team, device degradation rates under light and elevated temperatures are most instructive for understanding outdoor device reliability since in real-world conditions these individual factors act simultaneously to affect solar cell performance.
Their research findings are published in Nature journal under the title Towards linking lab and field lifetimes of perovskite solar cells.