The team at NREL used nanocrystals of cesium lead iodide (CsPbI3) in perovskite cells to reach an efficiency of 10.77%. While this is less then the current record of 22%, the design removes organic dyes and so boosts the lifetime of the cells.
The researchers discovered a method to stabilize the crystals in an all-inorganic perovskite material at room temperature that was previously only possible at high temperatures. Most research into perovskites has centered on a hybrid organic-inorganic structure, but the organic compounds haven’t been durable enough for the long-term use of perovskites as a solar cell. Using the inorganic nanocrystals opens up the use of the crystals for LED lighting and photovoltaics.
The nanocrystals of CsPbI3 were synthesized through the addition of a Cs-oleate solution to a flask containing PbI2 precursor. The NREL researchers purified the nanocrystals using methyl acetate as an anti-solvent that removed excess unreacted precursors.
This step turned out to be critical to increasing their stability. Unlike the bulk version of CsPbI3, which is unstable at room temperature, the nanocrystals were found to be stable across a wide range of temperatures, from well below 0°C to over 300°C, which is essential for both solar cells and LED lighting.
A thin film of 100 to 400nm was created from the nanocrystals by repeatedly dipping them into a methyl acetate solution, and used in a solar cell, this film showed the 10.77% efficiency in converting sunlight to electricity. This is a similar efficiency to record quantum dot solar cells of other materials and exceeds other all-inorganic perovskite solar cells.
The research was funded in part by the Energy Department’s Office of Science and by the SunShot Initiative, which aims to drive down the cost of solar electricity to $0.06 per kilowatt-hour. .
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