Episode 12: Europium thwarts reactivity in metal-halide perovskite solar cells

Research on perovskites has progressed rapidly for PV and LEDs, with new solar-cell efficiency records being set at a regular pace. There are hints of the first commercial products reaching the market by 2020, just a decade since perovskite photovoltaics were first discovered. MRS Bulletin presents the impact of a recent advance in this burgeoning field. Read the abstract in Science (doi:10.1126/science.aau5701).

Transcript
Welcome to MRS Bulletin’s Materials News Podcast, providing breakthrough news & interviews with researchers on the hot topics of 3D bioprinting, artificial intelligence and machine learning, bioelectronics, perovskites, quantum materials, robotics, and synthetic biology. My name is Bob Braughler.  

Metal-halide perovskite solar cells degrade when exposed to oxygen and moisture. Encapsulating the devices makes them more stable and long-lasting, but it does not solve one issue that crops up during regular device operation. Light, electric field, and thermal stress can all make lead and iodide ions more reactive, generating lead and iodine defects that serve as recombination centers for charge carriers and bring down device efficiency and lifetime. 

Researchers at Peking University have invented a novel technique for combating these defects. They added a rare-earth europium ion pair to lead-iodide perovskites. The redox pair shuttled electrons in a cyclical fashion from the defects, oxidizing lead and reducing iodine to recover lead and iodine ions. Devices with this redox shuttle have a power efficiency of 21.52%, and they retained more than 90% of this efficiency under 1-sun continuous illumination or heating at 85°C for 1500 hours. 

This work was published in a recent issue of Science. My name is Bob Braughler from the Materials Research Society. 

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