He, X. N.; Li, C. M.; Zhou, Y. S.; Cai, Z. X.; Zeng, X. Y.; and Lu, Yongfeng, "Enhancement of optical emission from laser-induced plasmas by combined spatial and magnetic confinement" (2011 Abstract: To enhance optical emission in laser-induced breakdown spectroscopy, both a pair of permanent magnets and an aluminum hemispherical cavity (diameter: 11.1 mm) were used simultaneously to magnetically and spatially confine plasmas produced by a KrF excimer laser in air from pure metal and alloyed samples. High enhancement factors of about 22 and 24 in the emission intensity of Co and Cr lines were acquired at a laser fluence of 6.2 J/cm 2 using the combined confinement, while enhancement factors of only about 11 and 12 were obtained just with a cavity. The mechanism of enhanced optical emission by combined confinement, including shock wave in the presence of a magnetic field, is discussed. The Si plasmas, however, were not influenced by the presence of magnets as Si is hard to ablate and ionize and hence has less free electrons and positive ions. Images of the laser-induced Cr and Si plasmas show the difference between pure metallic and semiconductor materials in the presence of both a cavity and magnets.
Additives are widely adopted for efficient perovskite solar cells (PSCs), and proper additive design contributes a lot to PSCs' various breakthroughs. Herein, a novel additive of N,1-fluoroformamidinium iodide (F-FAI), whose cation replaces one amino group in guanidinium (GA + ) with electron-withdrawing fluorine group, is synthesized and applied as the additive for PSCs. The electron-withdrawing effect of fluorine promotes the molecular polarity of N,1-fluoroformamidine (F-FA), enhancing the interaction of N,1-fluoroformamidinium (F-FA + ) with MAPbI 3 . Compared with the nonpolar GA + , F-FA + improves the crystallinity, passivates the defect, and downshifts the Fermi level of MAPbI 3 more significantly. The charge transfer and built-in field in printable triple mesoscopic PSCs are therefore enhanced. Moreover, charge transport in MAPbI 3 is also promoted by F-FAI. With these benefits, a power conversion efficiency of 17.01% for printable triple mesoscopic PSCs with improved open-circuit voltage and fill factor is obtained with the addition of F-FAI, superior to the efficiency of 15.24% for those devices with guanidinium iodide additives.
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