2,550 research outputs found

    Characterizing the Efficiency of Perovskite Solar Cells and Light-Emitting Diodes

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    Metal halide perovskites (MHPs) are being widely studied as a light-absorber for high-efficiency solar cells. With efforts being made throughout the globe, the power conversion efficiency of MHP solar cells has recently soared up to 25.2%. MHPs are now being spotlighted as a next-generation light-emitter as well. Their high color purity and solution-processability are of particular interest for display applications, which in general benefit from wide color gamut and low-cost high-resolution subpixel patterning. For this reason, research activities on perovskite light-emitting diodes (LEDs) are rapidly growing, and their external quantum efficiencies have been dramatically improved to over 20%. As more and more research groups with different backgrounds are working on these perovskite optoelectronic devices, the demand is growing for standard methods for accurate efficiency measurement that can be agreed upon across the disciplines and, at the same time, can be realized easily in the lab environment with due diligence. Herein, optoelectronic characterization methods are revisited from the viewpoint of MHP solar cells and LEDs. General efficiency measurement practices are first reviewed, common sources of errors are introduced, and guidelines for avoiding or minimizing those errors are then suggested to help researchers in fields develop the best measurement practice.

    Efficient Perovskite Light-Emitting Diodes Using Polycrystalline Core-Shell-Mimicked Nanograins

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    Making small nanograins in polycrystalline organic-inorganic halide perovskite (OIHP) films is critical to improving the luminescent efficiency in perovskite light-emitting diodes (PeLEDs). 3D polycrystalline OIHPs have fundamental limitations related to exciton binding energy and exciton diffusion length. At the same time, passivating the defects at the grain boundaries is also critical when the grain size becomes smaller. Molecular additives can be incorporated to shield the nanograins to suppress defects at grain boundaries; however, unevenly distributed molecular additives can cause imbalanced charge distribution and inefficient local defect passivation in polycrystalline OIHP films. Here, a kinetically controlled polycrystalline organic-shielded nanograin (OSN) film with a uniformly distributed organic semiconducting additive (2,2 ',2 ''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), TPBI) is developed mimicking core-shell nanoparticles. The OSN film causes improved photophysical and electroluminescent properties with improved light out-coupling by possessing a low refractive index. Finally, highly improved electroluminescent efficiencies of 21.81% ph el(-1) and 87.35 cd A(-1) are achieved with a half-sphere lens and four-time increased half-lifetime in polycrystalline PeLEDs. This strategy to make homogeneous, defect-healed polycrystalline core-shell-mimicked nanograin film with better optical out-coupling will provide a simple and efficient way to make highly efficient perovskite polycrystal films and their optoelectronics devices.

    Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an