Energy Focus
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team of researchers from China and the UK has made inverted perovskite solar cells with the highest recorded power-conversion efficiency of 20.9%, approaching that of regular architecture cells. Their study appeared in the journal Science (doi:10.1126/science.aap9282). Inverted cells have a simpler structure than regular ones. They are easier to fabricate, compatible with flexible substrates, and could lead to high-efficiency multijunction cells. But so far, their low
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he Achilles’ heel of perovskite solar cells is their penchant to decompose in the presence of moisture, oxygen, and heat. In a new study in Nature Energy (doi:10.1038/s41560-018-0192-2), engineers at the University of Toronto showed that local strains in the perovskite crystal lattice lead to defects, which ultimately lead to degradation because of their
Energy Focus Semitransparent organic PV generates power while reducing heat
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esearchers from South China University of Technology and the Chinese Academy of Sciences have developed a multifunctional, semitransparent, organic photovoltaic (ST-OPV) device that can generate electricity and at the same time block infrared (IR) light, which is responsible for heat generation. The ST-OPV would be capable of producing energy while reducing the overall consumption of electricity in a household or office. The heat rejection properties of the solar cell is comparable to commercial ones (NV-25, P-18ARL, and PR70). The work was reported in a recent issue of Joule (doi:10.1016/j.joule.2018.06.006).
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prevents exchanging halide ions and line up like peas in a pod. They produced an electrophoretic deposition method to assemble films of these peapod nanostructures on a substrate. The method led to the peapods forming
bundles that lined up vertically on the surface. By making single layers or multiple layers of different halide nanocrystals, the researchers made films that glowed different colors, including white.
open-circuit voltage has limited their efficiencies. The low voltage is due to the trapping of charge carriers at defects found at the interface between the perovskite film and charge extraction layers. The trapped carriers recombine without generating a photon. The researchers were able to eliminate this nonradiative recombination by using a two-step method to make perovskite films. They first deposited a mixed-cation lead mixed-halide
perovskite from solution, followed by another growth step using guanidinium bromide. This gave a wide bandgap near the top surface of the film and a more n-type bottom layer. Researchers believe the wide bandgap keeps charge carriers away from the top surface where defects exist and allows extra electrons that occupy the defects or traps for an n-type perovskite. Together, this reduces nonradiative recombination overall.
affinity for oxygen and water molecules. The researchers also showed that swapping some of the large ions in the structure with smaller ones can relax lattice strain and boost the material’s stability and performance. The choice of dopant is
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