NREL Research Reveals Importance of Simultaneous Conditions To Determine Problem Areas.
Testing Perovskite Solar Cells in “outdoor-real-conditions” is crucial to reach commercialization
Perovskite solar cells should be subjected to a combination of stress tests simultaneously to predict best how they will function outdoors, according to researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).
Solar cells must endure a set of harsh conditions—often with variable combinations of changing stress factors—to judge their stability. However, most researchers conduct these tests indoors with a few fixed stressing conditions. While these tests provide some necessary insight, understanding which stressor applied during indoor tests provided predictive correlations with outdoor operation is critical.
“We must understand how well perovskite solar cells will perform outdoors, under real conditions, to move this technology closer to commercialization,” said Kai Zhu, a senior scientist in the Chemistry and Nanoscience Center at NREL. “That is why we identified accelerated testing protocols that can be conducted in the laboratory to reveal how these cells would function after six months outside operation.”
Zhu is the lead author of a newly published paper, “Towards linking lab and field lifetimes of perovskite solar cells,” which appears in Nature’s journal. His co-authors from NREL are Qi Jiang, Robert Tirawat, Ross Kerner, E. Ashley Gaulding, Jimmy Newkirk, and Joseph Berry. Other co-authors from the University of Toledo collaborated with Zhu on several other recent papers about perovskites.
Outdoor conditions like humidity, heat, and even light will stress solar cells. As a result, the efficiency of solar cells declines, and power production decreases over time. To reach the reliability targets for the commercialization of perovskite technology, 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, a broad range of testing conditions exist, making it challenging to compare different studies and discern their relevance to achieving the reliability needed for commercialization.
The NREL-led research team put perovskite solar cells through a battery of tests. During the test for operational stability, the cells retained more than 93% of their maximum efficiency after about 5,030 hours of continuous operation. The 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 of about 5% degradation.
The tests addressed different stressors, such as light and heat, separately. However, in real-world conditions, these individual factors affect solar cell performance simultaneously. When combined, for example, light and heat significantly accelerate performance degradation or cause new problems that were otherwise absent or occur at slower rates when testing separately.
The researchers concluded that high temperature and illumination are the most critical stressors for understanding how well a perovskite solar cell will perform outdoors.
The U.S. Department of Energy Solar Energy Technologies Office funded the research.
NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for DOE by the Alliance for Sustainable Energy LLC.
This article is written by Wayne Hicks from NREL.
About the author
WAYNE HICKS, PUBLIC AFFAIRS SPECIALIST AT THE NATIONAL RENEWABLE ENERGY LABORATORY
As a highly-skilled, award-winning communication professional, Wayne Hicks has more than 30 years of experience in editing, writing, reporting, management, and design of print and online publications. He has a Bachelor’s Degree in Communication arts with emphasis on print journalism from the University of West Florida. At the National Renewable Energy Laboratory, Wayne Hicks is a Public affairs specialist with responsibilities that include responding to inquiries from the media, arranging interviews with NREL personnel, and coaching NREL staff as requested on how to deal with the media. Taking scientific research papers and writing press releases and feature articles about the work so that it is easy to understand and editing articles for external and internal audiences.
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