Jun. 21, 2018

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Metal-halide perovskites are semiconductors exhibiting physical properties highly beneficial for photovoltaic conversion of solar energy. Perovskite solar cells have already reached solar power conversion efficiency above 22%. Of particular interest is in the realization of stable tandem perovskite/silicon cells with efficiency over 30%. This development can be realized with a low additional cost to current silicon solar cell technology and could trigger a revolution in photovoltaics. 

However, unlike conventional solar cells, perovskite solar cells often exhibit significant performance variations during a day-night cycle as well as on the long term, which limits their commercialization. This makes quantifying the solar cell performance and stability challenge: If the efficiency drops during the day but recovers during the night (or vice versa), what is the cell's lifetime? How can the performance quality of different device architectures, with various diurnal dynamics, be compared? 

A multi-national team (Israel-the Netherland-Belgium-Denmark-Italy-Spain) led by the BGU group (Drs. Mark Khenkin and Iris Visoly-Fisher and Prof. Eugene Katz from the Alexandre Yersin Department of Solar Energy and Environmental Physics (YDSEEP) at the Jacob Blaustein Institutes for Desert Research (BIDR), recently reported a major advance in an analysis of the outdoor operation of solar cells, by proposing a new set of measurement standards. The new standards are based on outdoor measurements performed at the Solar Energy center in BGU's Sede Boqer campus, and account for both the long-term degradation and the reversible diurnal efficiency variation, allowing a broad comparison of different solar cell technologies. 

This analysis was published in the journal 'Energy & Environmental Science', where Khenkin, Visoly-Fisher, Katz, and coworkers challenged common concepts of traditional figures of merit for device performance and stability. This publication resulted from a collaboration in the framework of the EU-funded COST action StableNextSol (MP1307), in which Visoly-Fisher and Katz were management committee members. 

The article was named one of 24 "2018 Energy and Environmental Science HOT Articles" by the journal.

In another publication, the same team discussed possible mechanisms responsible for such reversible diurnal behavior. The research is an essential step towards developing stable and efficient perovskite solar cells.