As perovskite solar cells must be subjected to a combination of stress tests simultaneously to better predict how they will work outdoors, according NREL researchers (National Renewable Energy Laboratory) of the US Department of Energy.
The study pointed out that solar cells must withstand a set of harsh conditions – often with varying combinations of varying stress factors – to assess their stability, but most researchers conduct these tests indoors with some operating conditions. fixed stress.
While these tests provide some necessary information, NREL highlighted that it is critical to understand which stress factor applied during internal testing provided predictive correlations with external operation.
“We need to understand the performance of perovskite solar cells outdoors, in real-world conditions, to bring this technology closer to commercialization,” said Kai Zhu, senior scientist at NREL's Center for Chemistry and Nanoscience.
“That's why we identified accelerated testing protocols that can be conducted in the laboratory to reveal how these cells would perform after six months of outdoor operation,” he reported.
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External conditions such as humidity, heat and even light put stress on solar cells. As a result, their efficiency decreases and energy production decreases over time.
To achieve reliability goals for commercialization of perovskite technology, research has indicated that protocols must first be established so that improvements from different groups can be easily validated and compared.
Researchers tend to test the stability of perovskite solar cells by exposing them to light and under low temperatures. However, there is a wide range of testing conditions, making it difficult to compare different studies and discern their relevance to achieving the reliability required for commercialization.
Results
The NREL-led research team subjected perovskite solar cells to a battery of tests. During operational stability testing, the cells maintained more than 93% of their maximum efficiency after approximately 5.030 hours of continuous operation.
Such cells were subjected to thermal cycling, with temperatures repeatedly fluctuating between -40 and 85 degrees Celsius. After 1.000 cycles, the cells showed an average degradation of about 5%.
The tests addressed different stressors, such as light and heat, separately. However, in real-world conditions, these individual factors act simultaneously to affect solar cell performance.
When combined, for example, the report indicated that light and heat significantly accelerate performance degradation or cause new problems that would otherwise be absent or occur at slower rates when tested separately.
The researchers concluded that high temperature and lighting are the most critical combination of stress factors for understanding the performance of a perovskite solar cell outdoors.
