An international team of researchers led by Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) in Germany investigated combining continuous electric bias with dark storage as an accelerated aging test for perovskite solar cells. The aim was to assess ion migration-induced degradation modes, which are those defects that occur during extended outdoor field trials.
The work opens up room for “cautious optimism that we might be able to use electric bias for aging” and quality assurance tests for perovskite PV, according to Mark Khenkin, corresponding author of the research.
“Since perovskites can degrade differently from the more mature PV technologies, they require re-thinking of the tests we are performing. Here, we showed that an aging protocol consisting of electrical bias application and rest phases, both in the dark, can capture certain outdoor-relevant degradation modes in perovskite solar cells,” Khenkin told pv magazine.
In the study, the scientists aged glass-glass perovskite devices under prolonged forward bias at three stress levels in the dark. They observed rapid degradation when the applied voltage was slightly above the cell open-circuit voltage of 1.2 V. “To capture the complete dynamics of the induced degradation phenomena, we followed the 1.2 V forward bias phase with a post-bias rest phase, during which stress is removed, and the cells are stored in the dark,” explained the researchers.
During forward bias aging, the team noted that ion migration led to impeded charge transport, macroscopic defect growth, and an adverse response of the cells to short light soaking, all of which recovered in the post-bias rest phase, yet resulted in increased recombination due to redistribution of ions.
When it compared these dynamics to the results of outdoor tests of perovskite solar cells over a 20-month period in Berlin, Germany, similar patterns were observed. Periods of higher temperature and irradiance during spring-summer reportedly aligned with the forward bias phase and cooler, dimmer periods in fall–winter aligned with the post-bias rest phase.
“This indicates that dynamic ion migration is governed not only by diurnal cycles but also by seasonal variations,” said the researchers, asserting that the method offers a “single-stress, no-light approach to simulate dynamic ion migration-induced degradation outdoors.”
Because mass testing of industrial-sized perovskite modules under continuous illumination would be costly, the proposed accelerated aging approach could be a potential low-cost, high-throughput alternative to check resilience against dynamic ion migration-induced degradation modes.
“For the labs working with tiny prototype cells, it is relatively easy to conduct aging experiments under illumination,” explained Khenkin, adding that to capture outdoor effects on such devices, labs typically will use maximum power point (MPP) tracking under cycled light conditions.
“But on the full-area PV module, illuminating the device for many hundreds of hours is an expensive option that is rarely available. Electric biasing in the dark would be a simpler and cheaper approach by far, if it will prove to be universal and sufficient,” he said.
The team plans to continue the investigation of stability and reliability assessment routines to see, for example, how universal they might be across various device designs, or if other degradation mechanisms could be forced by this type of test.
The research consortium included scientists from Helmholtz-Zentrum Berlin für Materialien und Energie, Hochschule für Technik und Wirtschaft Berlin (HTW Berlin), Bielefeld University, University of Ljubljana, Ben-Gurion National Solar Energy Center, Ben-Gurion University of the Negev, and Université Grenoble Alpes.
Their investigation was detailed in “Mimicking outdoor ion migration in perovskite solar cells: a forward bias, no-light accelerated aging approach,” published by ACS Energy Letters. The study was also recognized in a research highlight published in Nature Energy.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: editors@pv-magazine.com.
By submitting this form you agree to pv magazine using your data for the purposes of publishing your comment.
Your personal data will only be disclosed or otherwise transmitted to third parties for the purposes of spam filtering or if this is necessary for technical maintenance of the website. Any other transfer to third parties will not take place unless this is justified on the basis of applicable data protection regulations or if pv magazine is legally obliged to do so.
You may revoke this consent at any time with effect for the future, in which case your personal data will be deleted immediately. Otherwise, your data will be deleted if pv magazine has processed your request or the purpose of data storage is fulfilled.
Further information on data privacy can be found in our Data Protection Policy.