Research Highlights: Perovskites
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RESEARCH HIGHLIGHTS :
Perovskites
By Prachi Patel Feature Editor: Pabitra K. Nayak
Perovskite solar cells are at the edge of commercial success. Device efficiency records break at a regular pace, while stability and optimization are progressing rapidly. The first commercial products could reach the market within the next year, only a decade since perovskite photovoltaics were first discovered. MRS Bulletin presents coverage of the most recent impactful advances in the burgeoning field of perovskite research.
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a ear-infrared (NIR) wavelengths b Ag of 1000–1700 nm have negligiMoO3 ble absorption and scattering in livMoO3 / Ag ing tissue, which makes this an ideal Porphyrin Porphyrin range for fluorescent probes used in medical imaging. Quantum dot (QD) Perovskite CQDS + perovskite + light-emitting diodes (LEDs) can emit TiO2 Ag2S@SiO2 light in this NIR window, but their ITO TiO2 efficiencies have been impractically low, reaching only about 8%. A new 1 μm ITO study published in Nature Photonics Glass (doi:10.1038/s41566-019-0526-z) shows the first QD LED emitting at a long wavelength of 1397 nm with an (a) Schematic illustration of a multilayered near-infrared-emitting quantum dot-in-perovskite light-emitting external quantum efficiency of nearly diode consisting of ITO/TiO2/perovskite+Ag2S@SiO2 quantum dots/porphyrin/MoO3/Ag. (b) Cross-sectional scanning electron microscope image of the fabricated device. ITO, indium tin oxide; CQDS, carbon quan17%. A perovskite matrix plays a key tum dots. Credit: Nature Photonics. role in the device’s high efficiency. To achieve this, the team, led by Abdul Rashid bin Mohd Yusoff at Swansea QD size,” Yusoff says. They incorporated of charges—where charges recombine University, made silica-encapsulated silver the QDs in a highly conductive yet passive without releasing photons—and ensures sulfide quantum dots with “careful control cesium-based perovskite matrix, which the speedy movement of charges, both of of both the shell composition/thickness and suppresses nonradiative recombination which increase efficiency.
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new technique to significantly improve the stability of tin-lead perovskite solar cells could pave the way for high-efficiency tandem solar cells. Tandem solar cells, made by stacking devices that absorb different parts of the solar spectrum, have higher power-conversion efficiencies than single-junction devices. For perovskite tandem cells, researchers typically use a wide-bandgap lead-based perovskite layer on top and a narrow-bandgap tin-lead perovskite layer underneath. But tin is prone to oxidation,
so the efficiency of tin-based devices drops drastically within a few hours in ambient conditions. University of Colorado Boulder Materials Science and Engineering Professor Michael McGehee and his colleagues reported that the commonly used hole transporter poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) reacts with tin-lead perovskites, severely reducing charge extraction. The team made a solar cell without a hole-transport layer,
with the
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