Research Highlights: Perovskites
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RESEARCH HIGHLIGHTS :
Perovskites
By Prachi Patel Feature Editor: Pabitra K. Nayak
Research on perovskites has progressed rapidly, with new solar-cell efficiency records being set at a regular pace. Perovskite manufacturer Oxford PV announced in December a new record certified efficiency of 28% for their perovskite-silicon tandem solar cell. The first commercial products could reach the market by 2020, a decade since perovskite photovoltaics were first discovered. MRS Bulletin presents a selection of recent advances in this burgeoning field.
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esearchers have made an all-perovskite tandem solar cell with a record high power-conversion efficiency of 21%. Tandem solar cells are more efficient than a single cell because each device in the stack can be tailored to absorb a different part of the light spectrum. Tandem perovskite/silicon cells are closer to market, but all-perovskite tandem cells would be easier and less costly. Making an all-perovskite tandem cell that is efficient has been a challenge. The bottom device in a tandem cell is prepared with a low-bandgap material to absorb all of the infrared photons passing through the top device. Despite many efforts, researchers have had difficulty making
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he presence of lead in state-of-the-art perovskite solar cells could hold back their commercialization. Lead-free alternatives based on tin compounds have shown promise, but they typically suffer from low efficiency and stability. Brown University’s Yuanyuan Zhou and Nitin Padture and their colleagues
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etal-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
high-quality low-bandgap perovskite absorber layers. Ag Yanfa Yan, at The UniC60/BCP versity of Toledo, and his 1.25-eV low-Eg (FASnl3)0.6(MAPbl3)0.4:Cl colleagues made a highPEDOT:PSS quality layer by introducing 2.5% chlorine into Ag/MoOx/ITO a mixed tin–lead perovC60/BCP skite. This increased grain 1.75-eV wide-Eg (FA0.8Cs0.2Pb(l0.7Br0.3)3 size and crystallinity of PTAA the layer and reduced ITO Glass electronic disorder, which quashed the charge-carA schematic diagram of the 2T tandem cell structure used in the study. Credit: Nature Energy. rier recombinations that produce heat and boost efficiency of the tandem cell. The cell s41560-018-0278-x) retains 85% of this reported in Nature Energy (doi:10.1038/ efficiency after 80 hours. have made a “surprising discovery” that provides a solution. Simply adding germanium to the lead-free perovskite cesium tin iodide (CsSnI3), which degrades easily, makes it air-tolerant, they found. Devices made with the new CsSn0.5Ge0.5I3 perovskite show an efficiency of 7.11% and remain highly stable after 500 hours
of operation under 1-sun illumination. The key to this behavior is the extremely high oxidation activity of Ge, whi
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